You can do it either way round, but you'll need to do it manually. If you ever get an upgrade, you can use the Barn Manager to consolidate horses, then fire all horseless riders
The savings has saved me a chunk of EBs - I have 4 accounts. I put the daily ebs in one, daily login ebs (when I get them), half my show profits in another ans the other has RO savings (that's on this account and SA) :)
Also when you have treats you will see an apple symbol in explore whivh you can click to boost the morale of your selected horse. Giving them treats outside of explore doesn't affect their morale