Question about Reer ByMySide

Not really.
The topper makes the support noticeable. And the spring part is too high according to me together with the topper (please measure!).

It's hard to say because I don't know what the bed is like. If the top mattress is very thick, it's certainly not ideal. And the protection has straps to attach to the base. So without a box spring, there's no safety.