PF 2nd ed will have a +1 per level treadmill on everything as it stands for now.
This is very bad thing as it makes low level monsters obsolete very fast and prevents players with good ideas and tactics to engage higher level monsters, because no matter how good the plan is, it will fail because of +1/lvl mechanics.
proficiency bonus should be 1+1/5 levels. You get increase at the same time with ability boosts.
training categories should be
untrained: -3 mod
trained:0
expert: +3
master: +5, min lvl 7
legendary: +6, min lvl 15
As you can see every step in training gives less and less bonuses so characters are encourage to spread their training around.
But some skills will be picked to legendary for access to skill feats.
Signature skills should go away or just be for legendary tier.
No proficiency bonus for AC.
Using armor unproficient gives -2 to AC, attacks, str and dex skills, dex saves and adds extra somatic casting action to spells.
this way 20th level character with 8 in a key ability would have +1 on a
untrained skill check and 1st level character with 18 in ability and training would have +5 on a skill check.
Currently with how advancing abilities work, maximum is 22 in an ability without magic.
20th level, 22 in ability(+6 bonus), legendary proficiency +6, level bonus +5.
That comes to a nice +17 bonus from starting +5 in above example.
Clearly an improvement, but not a HUGE difference.
By current rules it would be +20, +3, +6. That is +29.
Also magic weapons should give only +damage, not +attack.