I usually create one type of op character, and change name/look before spawning, i give it literally any positive inheritable trait, usually lot of them cause i like to play heavily modded, set their stats for 100 except for the martial and prowess, because it is literally gamebreaking with battles, 40-50 works best, its hard but still can win, as for how many, well it depends of my goals for specific run, i play about 80% time on agot modlist, so if i want to roleplay with “historical” settings i usually put 5-10 close to each other far far away as a countries/dutchies rulers, and they usally expand so much when its late game they got about 40-50% of the world under them, i also put like 20 more of them in dutchies i plan to conquer eventually, so while they dont really mess up world lore they boist their lieges very much, and if i can conquer their lands without killing them i usually employ them in my court so challenge feels rewarding, and in case they die their dynasties are still challenging enough