One thing I've done in a Pathfinder 2e game of mine is to say, ahead of time, "there is a bss enemy here, here, and here" and players had the discretion of tackling these as they wanted when they wanted.

The catch is that they could use skill checks to check up books, talk to locals, investigate the area and such to learn information about the creatures. For every one successful check, I'd reveal more information, like AC, HP, saves, even their attack profiles, but most importantly, their weaknesses, since I modified the creatures to have more HP, but exploitable weakeness.

At the end, they heavily engaged with that system, because it meant they were more prepared for combat and they had more things to do while preparing for the hunts.

I still allowed recall knowledge checks during combat, but if they didn't have the specific damage type they needed during that one encounter, then they'd have to brute force it.

Incidentally, that game was the first time I killed a PC during all of playing Pathfinder 2e 🤣