you shouldnt use bios from other cards, they are tuned to work with that hardware, its usualy same, but it may have different ram timings which will brick your gpu, or if u put bios from card which has better power delivery (pci-e power plugs/vrm design), than u may overload your psu/gpu/ or your mainboard
it is usualy fine if u go with same gpu board design even across different vendors where differences are minimal.
for example i used to have gtx 1060 from palit, and replaced bios with asus (both had same pcb), the only difference for me was that assus bios gave me 0rpm fan mode during low temperatures
as for overclocking, that is limited by your vrm/power delivery (or cooling)
and im 100% sure ITX gpus are low power design