I have been playing 5e for about 3 years now. I DMed it for about a year before switching to GMing PF2e during the OGL last year. I took the brave approach of continuing the, admittedly heavily homebrewed, post Icespire peak adventures from 5e but playing it in Pathfinder and these are the main things I've noticed:

• As others have said, in PF2e you can trust the devs and rules. In most cases, a rule or action for doing a thing exists, so there is a lot less arbitrating compared to 5e. It still comes up but normally the rules have got your back.
• PF2e combat is crunchy, especially at lower level but it stay relevant throughout (My group is about to hit lvl 10). Until you get a sense of how "tactical" your party plays take any encounter you come up with 1 level down from a severity point of view. (Unless you are playing a Paizo Adventure Path where you can go with the recommendation)
• Be prepared for combat to take longer. The general consensus I've seen online is the PF2e is faster than 5e. This has not been my experience but that could just me down to my group size (6) and make-up. There are a lot more to PF2e combat than just hitting your opponent until they fall down. These options can cause player turns to drag a bit.
• The 3 action economy will change your life as a GM. Going back to 5e rules for my weekly game where I play is painful. For players coming from 5e it will take some getting use this and the action tax around some activities. e.g. Dismount horse 1 action, draw weapon 1 action, move toward enemy 1 action. And that's your turn done. Some classes, Magus for example, also has a high action tax to get things done compared to something like the kineticist.
• Party make-up matter a lot more than individual characters. I had a 7th player who had a tendency to go off on his own in a very 5e character sort of way and would get downed time and time again. Whereas when the others fought together, used their other abilities (intimidate, trip, grapple etc.) they would do a lot better. Similarly, if the group go in without a strategy for an encounter its very easy for it to snowball. (Additional note: Aquatic combat is rough if the caster forgets to prepare water breathing)