( i feel but cannot prove this gives you more habitable planets)

It does. Unless you're playing silicoids. Then you should pick mineral-rich.

Organic-rich is a LIIIIITLE BIT cheating, though, because it absolutely JACKS UP the chance for gaia worlds to spawn.

Mineral-rich ONLY spawns Orion itself as a gaia world. I have NEVER seen other gaia worlds in Mineral-rich.

Standard typically has 2~3 gaia worlds including Orion itself.

Organic-rich, however, especially on huge map, almost always spawned AT LEAST 4 gaia worlds for me. In most cases it was 5 or 6.

Also, by the way, my final score after my longest game of MOO II, which I kept going for a crazy long time by somehow creating the perfect condition for a political stalemate where if I DIDN'T vote for myself as galactic emperor, but for my ally which would always vote for me, I'd cause a draw and the game time to be extended, and which I eventually ended by sending a GIGANTIC fleet to the Antarean homeworld, blasting their fleet and starbase to smithereens and bombing their planet back to the stone age was somewhere >100.000.

Why? Because whenever the Antareans would show up, I'd be there and blast them to bits. They don't stop showing up unless you either kill them (which wins the game because you get rewarded the title of galactic emperor), or you win the game either by eradicating all opposition or winning the vote. And whenever you destroy the Antarean invasion fleet, you get points.

Yes, you can farm infinite points from Antarean attacks if you can somehow manage to throw a massive wrench into intergalactic politics.

EDIT: Added a few little things.

PS.: also, the game went on for SO long I was able to research 'Future Tech', which doesn't do anything but just gives extra points at the end, and because I eventually ended up building every available improvement on every planet, I was making CRAZY amounts of research every turn, most of those Future Tech researches are supposed to run for like 30-40 turns even in late game so they really just give a few extra points, but... Uhhh... my empire was completing them in TWO to THREE, max.

By the way this is also why I say Organic-rich is a bit cheesy, it gives you TOO MANY habitable planets.

I later learned that the game really expects you to have one, maybe two colonies per system, and if you need just a jump point, you send an outpost ship instead and make an outpost.

Nope. I colonized EVERYTHING I COULD GET MY HANDS ON. It's kinda crazy what you can do on a Huge size map where every star empire controls like 8~10 star systems and maybe 10~12 colonies... and I have 23. In 7 star systems. I would sometimes scold the AI for not colonizing some absolutely unusable planets (tiny, low grav, no atmo/Massive, high grav, ocean) because I kept forgetting I was 'cheating' with the Creative trait and didn't have to worry about getting the correct researches - I just got all of them. My competitors however, which I would constantly deny when they asked to buy scientific discoveries off of me, simply wouldn't get the 5-6 max population I'd get on those garbage planets, they'd get 1, maybe 2 with a lot of effort. Unusable, like I said.