Since you say you're pretty lore oriented then i would start with DS1. It holds up. If you were just meh on lore then id say dive in with DS3 since that's my favorite fromsoft game

Highly recommend starting with beginner box. It's beginner friendly for GMs and players. There are two floors and each floor is about 3-4 hours.

If you have a good time then Abomination Vaults is a 3 book adventure that covers levels 1-10. It ties directly into Beginner Box if you want or you can start Abom Vaults with new characters and from the very start. Abomination vaults is a mega dungeon so lots of combat opportunities, but it also has lots of roleplay potential too depending on how the players approach each floor.

I like to think my rules aren't sketchy, but the closest would be for character building my rules for uncommon and rare options are "tell me a story i can't say no to"

For uncommon options I'm pretty willing to take anything as long as it's not just an obvious power grab. For rare stuff i look more to see how much thought they've put into it and if it would negatively affect the rest of the party.

End result: I've had some pretty freak tables and others where everyone sticks to core ancestries.

I'm not sure id define it as "favorite", but when i think about this the most memorable skill check boss that comes to mind for me is Dancer (ds3). Whether you accidently come across her early or doing it later she can be a considerable fight. Though unfortunately she can be cheesed so it does lose some value from that

I wonder if there will be a new slayer iconic then, since it seemed they used the pf1 slayer iconic Zadim for the pf2 Avenger class archetype

Haven't played demon souls. Didn't love elden ring. Of the remaining DS3 is my favorite but part of that i think is just because it's the most familiar. Sekiro and bloodborne i loved as well. If i had to choose i think bloodborne 2 because id love to see more of that story the most alongside new atrocities, and i really loved the layers of exploration/shortcut it brought.

I'm curious, when you say sekiro has so much untapped potential, does anything in particular come to mind?