I think any can theoretically work (And we're also disregarding instances like a taur whose lower body is an arthropod derived form where you could have up to like a 100 or more) but four still works best from a simple dynamic posing and design perspective for me - there's so much space in there already, and six limbs overall is already a lot to handle
As for how many i'd like... I mean, yeah, four seems good, esp. since my ideal approach is probably just "a literal horse" for max versatility