>>96776192
>>96776668
But seriously speaking, I will tell you, the bulk of the customizability you're looking for comes through feats.
Assuming you're used to 5e, in 5e, your Champion Fighter is GUARANTEED to have exactly the same features as every other Champion Fighter. You get some choices to differentiate yourself, such as your fighting style or the artisan's tools I think Champion Fighters get to pick, but it's not much compared to Pathfinder.
Same goes for races/ancestries. There's a TON of ancestry feats in Pathfinder. In D&D, your tiefling will be exactly identical to every other tiefling, but in Pathfinder your tiefling might be descended from a devil or a rakshasa, and those differences will allow you to pick up different abilities later on. 2 tieflings in the same party very likely won't be the same, and in Pathfinder tiefling is a heritage and not a race like D&D, so you can get elf, dwarf, human etc. traits on a tiefling as well.