Biped-Quadruped rig

Hello folks!

I would like to model an anthropomorphic character, which can also be “turned” to quadruped - walk on four legs.

I’ve already done some anthropomorphic characters but those are mainly only biped characters.

So, my question is, what would be the best way to model/rig a biped character which can turn quadruped and vise versa? Would it be better to model the character quadruped and then just weight paint the “details” when biped? Or would it be better to model it biped and weight paint the “details” when quadruped?

Should I add “extra” transformation bones to the rig?

I know that every modeler does what they are most comfortable with, I’m just askin what do most people do and what would actually be the more “flexible” way?

It would be much more easier just to make two separate characters with two separate rigs. One for biped form other for quadruped form.