I have a 4 tank 4 vented fuel cap Savannah S.
I only experienced once venting of fuel from on overfull tank - caused by not flying level over an extended period (and exacerbated by fuel return into that tank).
In my experience, the movement of fuel between tanks is gradual and slow and not instantaneous so while in theory the problems you pose are there and real, in practice they should not materialise unless as you say you park on uneven ground or you fly one wing down for a long period.
I don't have experience with check valves but they sound like a good idea. I have seen a Savannah in flight where the right outboard fuel tank cap came off in flight. The ensuing vacuum was so great, fuel would erupt from the tank every 30 seconds and was sufficiently strong to drain dry all four tanks!