Boost mode will do whatever it is set to by the developer.Playable, yes. But will the ps4 games I have bought on PS4 transfer to PS5? Since I have almost a completely digital library.
If there's a pro/PS5 patch, it should use the whole GPU. If there isn't, it should only use half the GPU.
They said 99% of games will be playable. Why would that exclude digital PS4 titles?