I can say with certainty and confidence you can 100% successfully play without min/maxing your prime stat. with non-optimized PC's, we have not had an unending blood-bath of PC deaths. We have had 26 sessions of Fun. Close calls, not 1 PC perma-death, laughter, hijinks, great role-playing, the ability to attempt and succeed and fail at non-core abilities, to sneak past guards, to negotiate out of fights, to swing across chandeliers, chases through dungeons, and merging encounters into session long running battles.
In short, everything I love about fantasy role-playing is not only allowed, but actively supported in PF2.
If your prime stat was supposed to be at max, and this was "by design", don't you think the designers would have, you know, created a char-gen process to enforce this? This assertion, and other statements about the "one-true-way" that PF2 must be played, my first-hand experience in every instance becomes the counter argument as to why these facts are simply stylistic choices. But don't mistake what I just said as the one-true-way either - my choices are also stylistic and I only included as illustrative that there are other ways the PF2 can be played.
PF2 is the most dial-rich version of D&D I've ever played. By "dial-rich" I mean inbuilt support for dialing up or down rules, complexity, difficulty, and adherence to the various rule subsystems. <-- right here is what past me would have loved to have heard future me say, so I didn't obsess so much about learning it all, all at once.
The OP asks what should a 5e DM consider when moving to PF2? Though I did add some feedback in earlier posts, I would say the following as a general statement. Depending on your group's play style (my group is VERY free-flowing with Rule of Cool being most important), I would suggest the following:
While PF2 supports a much more rules heavy approach to game-play, it does not need to - and the game does fully support a much more rules-light GM Fiat mode of play similar to 5e. Don't bog yourself down with trying (initially) to memorize all the conditions, or modifiers or traits or feats. You really only need to understand the -4 to +4 range for penalties/bonuses with +/- 1-2 being the norm and keep the CRB tables 10-4, 5 and 6 handy for quick reference. Otherwise, simply knowing what the top line skill and attribute definitions are without fretting over specific skill actions, you will be 100% fine and will have a great time playing PF2.
It really can be that simple. (if you want it to be)
Cheers,
J.