Rule variations between PF1/3.5 - Stacking

[Lorddenorstrus]

So; For many years I played specifically 3.5. Eventually mixing PF1 in. As MOST things appear to be the same with few variations. Besides some obv class changes. Were any base rules that I am unaware of changed going from 3.5 to PF on how typings stack. ??

Recently was debating with someone the rules legality of stacking modifiers. Because for some reason they thought you could only gain an X to Y once. Example Nymph Scaled Fist monks wouldn't be able to get Cha to AC twice. This person thought it was "Armor + Cha ability mod + Cha ability mod" not stacking. Correct me if wrong but do not the abilities retype the ability modifier to be a different source which is how stacking works to begin with? Monk changes X stat to be Miscellaneous bonus to AC. Nymph gives Cha mod to AC but as a Deflection typed bonus.

because the original debate was the Oracle ability that rekeys Dexterity ability modifier to be keyed of Charisma. It's still categorized as Dexterity modifier is it not? Just numerically changed to a different source. So a Misc / Deflection typed bonus even if they key off the same stat as different typed bonuses should stack. Unless my understanding of stacks has been vastly wrong for many years.
I mean we have Enhancement bonuses to natural armor.. and regular Natural armor stacking as it's 2 different typed Natural ACs...