The AGM battery is a starting battery and should be used for the engine. It supplies high current for a short time. The golf cart batteries are deep cycle with higher storage capacity and like longer term smaller loads like what you have in the house section of the coach. The disconnect switch can go on either side of the battery. Mine is on the positive side.

That disconnect switch is what saved me when I had an engine fire many years ago.

I accidentally hit send in the previous posting before I had finished typing.