Apart weapons , you have to sell armors, bolts, horse equipment and hides. These are the heaviest things. Then check the junk

Why don't you just drop the stuff in an easily accessible place? By all accounts, stuff dropped on the ground by the player doesn't get cleared..? I think there are a handful of confirmed storage places as well.. like a house in Skellige that someone did some testing on to see if it ever got cleared by the system and it never did..

Not entirely true. If the state of the area changes (i.e. people or props move), the game seems to wipe all objects in the area and replace them with the new environment.

If your shiny, expensive, really heavy Ursine armor happens to be sitting just inside the front gate of Kaer Trolde while having a feast... don't expect it to be there when you get back. This means that while huge areas of the game seem to be safe, you can never really predict which houses/streets/mountains will suddenly become the place the game needs to put a group of bandits, a burning house, or a horse race.

My best advice if you want to try this is to go back to an out of the way marker post that you've already done a quest near (anywhere in White Orchard will probably work), and put things there. Just in case, manual save every once in a while.

I'd assumed nothing on the ground was safe, like it was in TW2 since enemy loot bags don't stay around. Sounds risky still.

From my experience finishing the game I have to agree with your assessment here. Armor, swords, exploding crossbow bolts, horse gear, trophies and various hides in particular bear hides are the heaviest individually. Some other things aren't heavy individually but you get a lot of them and they add up to being heavy too.

For the most part food and ingredients for alchemy are very light, many/most such items weighting 0.01 which means you can have 100 of them and it only uses 1 unit of weight. But... there are well over 100 if not close to 200 different ingredients and while they're all individually only a small fraction of Geralt's encumbrance, they do add up. So it is a good idea to purge excess ingredients/items from time to time. There are some things that are harder to find or which are used a lot such as alcohest that I'd keep 25-50 of when purging, and I also found arenia and barbicane fruit to be hard to find at times as well as monster feathers and a few other ingredients so I tended to keep many more of those when purging - but most ingredients I ended up only keeping 5-10 max of each purging session.

By far the biggest impact on weight is the first tab and last tab of inventory though with the items listed above, so it is a good idea to offload them sooner rather than later.

Also, at a certain point in the game you end up with more money than you could ever possibly spend to good use. Once you have 40000 or more cash, you can just start purging by dropping crap on the ground everywhere that you would normally sell for cash. Just don't drop anything you may regret leaving behind - only drop shit you definitely 100% don't care about, which is most crap. If there is the slightest chance you might need or want something again then sell it at a vendor you favour such as the ones at Crow's Perch or Novigrad, which were my preferred vendors in game. If you change your mind all vendors seem to hold on to the reams of crap you sell them and nobody else ever buys the crap from them. I'm surprised they don't go bankrupt from poor cashflow management but then this is a fantasy game and not an economic simulator too so... :)

If I could make one single genie-wish change to the inventory, I would have the game sort all of the books to the BOTTOM so that it goes oils + bombs + potions + decoctions + books instead of the current item sort order. Having to scroll 10 pages over books and crap to find potions is annoying if you hold on to all the books/notes in case you need them or for some other reason. :)

I can be, just try to keep in mind what's happening (or, probably happening - I'm not a dev).

The game will have several states for a given area.
- Original state
- Current state (with your dropped loot scattered everywhere)
- Quest state (with specific NPCs, props and monster bodies the cutscenes prevented you from looting)
- Post-quest state (probably the same as "Original state", unless the quest did something to the terrain, like burnt a house down)

When you trigger a quest, the "Current state" gets deleted and replaced with "Quest state". When the quest is over, the "Quest state" is then also deleted, and replaced with "Post-Quest state". Note with this, your "Current state" with the 400lbs of gear you wanted to get rid of never comes back.

The problem is you can't tell which places have untriggered Quest states just waiting to eat your gear. That's why I mentioned White Orchard - chances are good you've already cleaned out all the quests there, so your gear should be safe.

Just a side note: monster feathers can be obtained by dismantling harpy feathers.

About the rest you got the point.

Yep, many things can be created via dismantling although it's a little tedious too, but less so than travelling from one merchant to another in a quest to find an item you might already have on you by dismantling. :)