-Keeping the map smaller helps too. (there is a mod that lets you set the map resolution. I made mine to fit YT aspect ratio so there is no useless space that calculating in the back ground.
-Also don't over do the overflow with items pawn or livestock. Its nice to have 5 years worth of food but it does come ad a cost. same goes for weapons clothing, corpses and anything else that can decay. I keep my base around 20 to maybe 30 (after that i lose track any way of who is who and it becomes more like dwarffortress) and try to keep a year of food and around 5 sets of clothing for renewal. And i actively trade away the overflow for silver and goodwill. For the animals consider up sizing the animal type. its much easier for the game to handle 10 alpaca then it is to keep track of 50 egg laying critters.

2/2
I never played sos2 thou do you move on from playing on the planet or do you keep 2 "colonies" active? if you have more then one base then that is quite intensive
My most intensive mod would be rimworld of magic, with all its bars and auto casting stuff. but if you don't give every pawn loads of auto casting options or minions its not that bad.

There are some general things you can do to keep the game running smoother.
-like have less things to calculate in the background. by first of settling somewhere where there is little. maps with mostly sand. deep water or solid rock have nothing to calculate but some random grass and a single tree. Also more lush places have much more animals spawning, which also leads to more carcasses that all have timers and hp to keep track of. (you can still path the forest and or burn it down to give a little boost if you need to but not having it in the first place is better in the end.)

1/2
there is always a significant performance lost in the end but nothing i would quit over. i do keep it on max speed (which does feel like normal speed near the end, i don't know the fps)
I don't use cherry picker mod

I do make the game fun for me. Even if it means disabling some aspects that i don't enjoy. Some of them like arial raids go against spawling build so i took them out. I also don't shy away from giving myself a break by playing on peaceful for some time. Especialy near the end where there is only terraforming to be done and it becomes boring. or simply reloading an older save if the game wands to go a warhammer route with 3 mech drops and a siege.
I am very picky about who enters the base, yes. I also disabled the random "wander join" events. most people come by the hospitality mod. it gives you a neat way of recruiting useful pawns.

What I really need to know, is how in the hell did you manage to finish this? Was your TPS anything close to 60 @ 1X speed? How were the other speeds? Are you using Cherry Picker?

I'm asking because I play maps like this and "TRY" to make extremely detailed and complicated bases.. and I love every minute of it, but I inevitably run up against performance loss so massive that I'm forced to abort.. I'd love to take mods like SoS2 further into fleet actions, orbital bombardments and planetary domination-style gameplay but even using powerful mods like Faction Manager 1.4 (the one that lets you load and unload colonies on-the-fly inside of a running game) and all the various well known performance mods I still manage to grind myself to a crawl every single freaking frustrating time. I know it's because of something I'm doing wrong I just can't seem to figure out what it is.

Cool thanks for the input, I love this game.

Water, or rather terraforming is done with Fertile fields mod. but does not work nice with modded terrain (like from alpha biomes).
Some mods i can't do without is the ceramics mod for pure white floors and walls and dubs paint mod for the colors. the combination give the most vibrant colors.
Rimworld of magic is kind of a theme setter, just pick a class and build around it. get more mods in that fit the theme.

Nope, I just see that as a dream map, and you solved that issue. The rest is most likely for flavour.

Unless that's water I see added in, that would be the only other mod. Unless there's some 'cant live without' ones

Thank you very much.
yes i know. kinda on point thou, small mod list with a trigger warning :P
Mod list are rather useless anyway, without context of why I added them, how I used them, the personal setting and what to avoid when combining certain mods.
But people always ask for them so, there it is in its 5 sec of glory
If you have specific question I would be happy to help.

Have an award.

Thank you, sir. Your mod list at the end was too short to see lol.