Remote Play from PS5 to PS4 slim

I own both a PS5 and a PS4 slim, and I've been trying out the Remote Play feature to play from another room, but I have a few questions. Would I be able to play games set on 60fps or would it always "show up" as 30fps? Why do some games (for example FF7 Rebirth) look super laggy, while the main PS5 menu and other games look completely fine?