what's the minimum i need to run Persona 5 @ a stable 30 fps

If it supports TSX, that's an even bigger boost. Unfortunately, only a handful of CPUs can use TSX. In terms of recommendation, at least a 7th gen Intel should suffice. I use a mobile i7-8750H and it's been really good with Gran Turismo games surprisingly considering that the series is known to be graphically intense in the post-PS1 era.