I don't believe there's a wild splendens. possibly folks are just breeding a little irate ones?
wild bettas are just a way of saying species that are not splendens.
Wild hybrid, or alien bettas are hybrids between differing species of wild betta (maybe splendens too)
water parameters, temperature and otherwise will depend on the specific species. I think domestic splendens would be OK a bit higher, it may be too high for some wild types (ours are all room temperature, low 70Fs)
read up on the specific species, even domestic splendens.