You may want to be a little clearer. Are you after a mix of the old style Reddit interface alongside what RES added?
If so I can’t remember what RES added, but I gather it’s enough that the old style frontend may still feel lacking and the others aren’t scratching that itch either.
Whenever you like, honestly. It’s mostly a nice acknowledgment to the poster that you appreciated their post. Unlike commercial social media it’s not sending out anything to your followers that you interacted with it (at least last I checked).
I think many people boost more than favorite because it functions a little similarly in regards to acknowledgment, with the bonus that it helps share the post to others which is even more relevant in federated networks than on centralized platforms.