Et Tu and FIXT both have numerous bug fixes left even in the vanilla game with the unofficial patches, yet both also add a lot of new content, some of which was cut from the final game when it was first released. Et Tu allows you to play with the Fallout 2 engine and allows you to enable certain content from the second game, including new critters, weapon upgrades, cavern maps, a vehicle, and satellite locations. FIXT adds a lot of new content. Both also allow you to get a good ending for the Hub and Adytum. For vanilla with the unofficial patches, you'll need the Good Endings Restored mod to do that, but I can't find it for download anymore anywhere.

Recently, I had tried FIXT with a patch that was supposed to correct certain errors, but I didn't really care much for the new debug menu when I interacted with the Vault 13 computer outside the front door.

Right now, I'm using Et Tu as a new official version of FIXT hasn't been released in years and its latest version still has many bugs and problems. ET Tu seems to offer a better experience, though I disabled much of the unique content because I wanted to keep the feel of the original game, including the motorcycle, caverns, critters, etc. While I appreciate the fact that you can push your followers out of the way if they block your path, I can't figure out how to disable combat control or the npc mod that allows them to change their armor and level up. Since I dump Charisma, I found that I can't get Aradesh to tell me about other towns, he just gives me a Dharma saying about not heeding the call of the wolf when the fox is raiding the hen house. When I talk to Ian, he no longer has any reply when I use the TMA feature to ask about the named residents of Shady Sands, and when I ask him about Killian, he says, "That's me." And stealing Neal's urn is harder because he reacts to noises when he is in his room, though I found that I can enter combat mode, steal the urn, and then leave before he can react to such noises. The only thing I have enabled is the cut characters from the vanilla game. I do like the fact that I can report Iguana Bob to the police, the ability to ask the head scavenger in Adytum about the parts when directed to him by Miles, and other new dialogue. However, I can't get the option to talk to Saul about Trish, even though I've been friendly to him, witnessed the incident at the bar between Trish and the Skulz, and talked to her about why she screamed his name.

For a purist for me, which is the best way to play the first game. With Et Tu? FIXT? Or vanilla with the unofficial patches?

Et Tu currently is a mess, because new controversional content being added before all the FO1 specific features are implemented. I do not recommend it for a general playing.

FIXT comes as a Full edition and Fixes only edition. And, while Full edition adds redundant content (more suitable for a mod), the Fixes only edition is really close to the full set of unofficial patches by TeamX. The most notable differences are sfall and hi-res patch bundled with FIXT.
Sj, the real choice is between FIXT (Fixes only) ans TeamX patches. FIXT has more bugs squashed overall as a more recently updated project. But unlike TeamX patches, it also 'fixes' some things which can not be verifyed as a clear bugs. Some of those 'fixes' are even just a fill for a popular demand from the community. In this sense unofficial patches are more purist.
If you chose FIXT the installer will guide you. If you chose unofficial patches by TeamX, the you install everything strictly in the following order: semi-official patch v1.2.1 RC; unoffical patch v 1.3.5; NPC mod v3.5 (optional, since not a bugfix at all).

You can try this compilation https://www.nuclear-city.com/index.php/topic/992-fallout-1-unofficial-patch-136/ (google translate it),which is basically just teamx patches + sfall + some small fixes like cathedral fix and children fix in a form of an installer.

Thanks, I'll give that a try.

By the way, if this installer restores good endings for the Hub and Adytum, and since I'm the type of player who likes to level grind at the Deathclaw warehouse until level 21, get all implants (except Endurance if it is even as I get no bonus for an endgame odd value), and do all quests (good if good, evil if evil), what should I set the number of days until the invasion for Adytum and Hub?

"HOW TO MODIFY THOSE TIME LIMITS:

If you want to change the days until invasion,
modify these lines in Fallout\DATA\DATA\VAULT13.GAM:

FOLLOWERS_INVADED_DATE :=90;
THE_HUB_INVADED_DATE :=140;

Note, changes to these two invasion values WILL ONLY AFFECT NEW GAMES!"

You can check the readme for more info.

I've changed all the dates since I installed the Restoration Mod as part of the 1.3.6 patch. I want to have enough time to complete all quests for my karma route (good or evil), get all the implants, level grind the deathclaws in Adytum, and get all the special encounters with very high luck, especially the one with the Alien Blaster as that's the best gun for killing the Deathclaws.

Here's what I changed the invasion dates to:

Adytum: 250
Necropolis 260 (They'll still invade 30 days after the mutants at the watershed are killed)
Hub: 270
Brotherhood: 280
Junktown: 290
Shady Sands: 300

I started with 250 for Adytum as that's when the game would have ended if I still hadn't found the water chip after the extended deadline given by the water merchants ended. Which means that this is the new date of invasions according to a date calculator I found online:

Adytum - August 12
Necropolis - August 22
Hub - September 1
Brotherhood - September 11
Junktown - September 21
Shady Sands - October 1

Since I tend to have killed the Master by as early as late June or mid July, I figured this gives me enough time. If anyone has a better idea on how many days I should set each, let me know.

On my end, there's no delay in combat.

As far as the other points go, that's just teamx behavior no?

I've never had either of the other problems with just the TeamX patches. Recently, I played the game with the TeamX patches and SFall. I didn't have the first or second problem, but still had the third. Something with SFall maybe.

The first one is just vanilla behaviour, teamx 1.3.5 behaves identically. The gun is reloaded by the ammo stack that's topmost. You can see it in this video (teamx 1.3.5) -> https://streamable.com/3a5ftu
The compilation has INV_ADD_ITEMS_AT_TOP=1 set in f1_res.ini as the default value, which puts items at the top of the inventory stack instead of the bottom. Maybe this is what confuses you? If so, change it to 0.

The second one, well I don't have such an issue, that said if you're playing windowed mode, you have to set EXTRA_WIN_MSG_CHECKS=1 in f1_res.ini, otherwise there is a pause between turns. But I don't think this concerns full screen mode.

The third one is just a vanilla bug that's not fixed in teamx. I think it's fixed only in FIXT .

I have gotten positive reactions from npcs with either high Charisma or very high reputation with the TeamX patches. One time, I started with 10 Charisma, got the reputation bonus from the Shady Sands cooki after complimenting her meal. When I spoke to Aradesh, he had a completely different introduction with his smiling face. Tandi also was willing to give out more information when I asked about stories from down south or other towns. Even if I started with only 1 Charisma, after getting a high reputation and the Champion reputation, when I first spoke to characters such as Laura, Harry, Set, Vree, Jacoren, etc, they were all smiling as I had a positive reaction. But the last time I played the game with the Sfall, when I spoke to Set for the first time with high reputation and the Champion title, his face showed a neutral reaction.

Ah, I misunderstood your post, I thought that you immediately had a positive reaction from Aradesh. But you only had it after complimenting the cook. Well here's Aradesh reaction after complimenting the cook with sfall https://streamable.com/9qcoxj on a 10 CHA character. Vanilla has the same reaction.

As far as Set is concerned, well the best way to investigate would be to do 2 identical runs, one in vanilla and one in teamx and compare Set's reaction. Other than that there's probably not much that can be done.

Why isn't Aradesh smiling if you've gotten a positive reaction?

Yes, you are correct. It seems to be that newer sfalls have this bug in them. 1.7.6 works OK as far as reactions are concerned. https://www.mediafire.com/file/hlah5435064z9qj/sfall1_v1.7.6_unofficial_by_Crafty.7z/file

this version of SFall won't work with 1.3.6.

What version of SFall will work and still have the correct reactions from npcs?