PF2 does not have a lightning quick levelling system.
I wouldn't call it "lightning quick", but it is
surprisingly quick – primarily because of efficient siloing. In most cases, you have two choices to make every time you level up. There's a four-level cycle that goes like this:
2: Class feat, skill feat.
3: General feat, skill increase.
4: Class feat, skill feat.
5: Ancestry feat, skill increase.
+4: Repeat. This is the same for every class except Rogues and Investigators, who both get skill feats and skill increases every level.
Class and ancestry feats are usually chosen from a list of about 5-10 options (of course, with more expansion books this goes up). In many cases, you are strongly incentivized to take one particular option because it improves one you took at an earlier level – e.g. a monk with Mountain Stance doesn't
have to take Mountain Stronghold at 6th level, but they probably want to. Technically you have more options than this because you can go back and pick options you didn't before, and you have archetypes which vastly increase what you can do with a class feat, but those are "opt-in" complexity. They are basically the equivalent of multi-classing in 5e.
Skill increases can technically be taken in any skill that hasn't hit the ceiling yet (there are like 15 skills, plus Lore which is an umbrella skill for all sorts of narrow knowledge skills), but I've never seen anyone dither all that much about it. You generally know what skills you use a lot and need improving.
What does take time IME is choosing general feats or skill feats. Both of these are fairly open-ended, and at least at lower levels you might not have much to go on when choosing what to get. Things tend to narrow down somewhat at higher levels because by then you (a) have a better handle on your character and what they want to do, and (b) have probably improved some of your skills, and you'll likely want to have skill feats that take advantage of those improvements.
Another thing that takes time when leveling up is book-keeping, at least if you're sticking to pen-and-paper. Pretty much every calculation in the game uses your level as a bonus, so all those values will need to be adjusted by one point (or three, if you also increased the proficiency the value was based on). And spellcasting of course adds some choices about which spell to take.