None of the listed DLC on the base game listing are included in the Nova / Galaxy editions (with the POSSIBLE exception of the soundtrack in the Galaxy IIRC - though it may be a cutdown varient compared to the separate DLC)

It is bad page design by GOG not to mention this and not list them / make them purchasable on thehigher tier edition pages

I was going to buy Stellaris Galaxy Edition + DLC regardless of the price, so I bought them separately and checked before buying the DLC.

Short answer: The only DLC included in the special editions (Galaxy and Nova) is the soundtrack DLC. The special editions include the full soundtrack, same as the equivalent DLC does. It's not a cutdown variant as it has 47 tracks, which is the same number that the soundtrack DLC claims to give you on its store page.

Except for the soundtrack, all other DLC must be bought separately even if you purchased a special edition of Stellaris. I confirmed no DLC was baked in by launching the game and starting a new playthrough. I didn't see any option to start a Machine Empire, which Synthetic Dawn should have given me.

Included some quick screenshots from GOG Galaxy after I bought only Stellaris Galaxy Edition and nothing else.

Hope that clarifies things for everyone with this question.

Here is a list of the DLC's on Paradox's website:
https://stellaris.paradoxwikis.com/Downloadable_content

I nearly didn't purchase this game (despite the good introduction discount), because of the huge number of optional DLC's (which does make it rather pricey if you purchase them all at once).

After spending a bit of time researching the different DLC's, and after two occasions in which I just ended up removing all of them from the cart after being overwhelmed, I finally ended up purchasing the Nova edition (OST + Arachnoid Portrait Pack)...and then caved in about 20 minutes later and purchased 3 DLC's.

There isn't much of a consensus on which DLC's are worthwhile, except for perhaps "Utopia", so I ended up purchasing:

Utopia: Just about every buyers guide recommended this. Since I'm new to the game, I don't really know exactly what most of those features are, but it does add huge construction projects (Dyson Sphere's, Ring worlds).

Distant Stars: I think this adds multi star systems (binary, trinary), and improves exploration (anomalies). That's pretty much why I went with this, even though I wasn't sure exactly what this was adding having not played the base game.

Leviathans: Not too expensive and this often came up as a recommendation (not as much as Utopia).

Apparently "Utopia" is regarded as an expansion, and both "Distant Stars" & "Leviathans" are story packages (see attached image).

I can say though after 2 days of owning the game, it does seem a pretty well put together, although I think the default difficulty is still too high for a beginner (Pirates were far too powerful playing my first game when I had no idea what I was doing, so I had to end that game and start another). I'm on my second game now, and while I know a little better what I'm doing, the AI is leagues ahead of me, and starting to cut me off from being able to freely explore (also habitable worlds are insanely rare as I've only found 4 (3 of which I colonized) in my current playthrough).

Question. If I buy this dlcs later, will they work on Games I already started too or begin their events start with a new game?

Utopia is the option to build big things and is mostly mid game stuff... i.e, playing as star wars = build things the size of the deathstar

Leviathans is the big space dragon etc but people grab it for the extra shop options... again it mostly mid to late game when you have too much money and nothing to spend it on

Distant stars is for people that like to roll dice, it may be a good idea to open that box but something really bad could also be inside

they are in order of best to worse and everything else is fluff... take it if you want it but don't stress about not having it

@Koroton = yes and no, yes you get the dlc items in any game you are playing but no it does not change what is already in the game so for example Utopia would allow you to build a new place for your people to live but getting the machine races will not add them into this game because all the races are already there... even if you didn't run into them yet

I was interested in getting this game until I checked out all the "DLC" content. You get the entire game when you purchase the base game. The "DLC's" seem to be missing files that unlock the parts that were chopped out of the game to be sold later in pieces. Check the size of the downloads for all the "DLC's" and you will see what I mean.

It's boils down to (in my opinion), they made a game, then chopped it into parts to sell piecemeal.