You can also consider a B360. Z370 and Z390 should be compatible out of the box without updating BIOS. But always check on the manufacturers site.
You'll probably be fine on the RAM side. If in doubt, check the manufacturers QVL which will be on the motherboards support page. But if the RAM isn't on there, it doesn't mean it isn't supported - the list of available RAM is simply too big for a QVL to be updated to match.