As stated above, wet in wet is far better than fully cured laminates on top of each other.
Wet means that the laminate is still very slightly tacky and not fully cured.
Use the peel ply only on top of the last layer. It creates a resin rich surface which can more easily be sanded. You will also take less glass away from the last layer this way.
If you use it in between layers, your laminate contains far to much resin.
Interlaminar shear strength is terrible in this case.
Peel ply in between is never a good idea. If one accidentally misses to peel it fully, you end up with an in built weak spot.
Never use mat with Epoxy.
Mat is usually made with a binder which is designed to break up by the Styrene inside Polyester Resin.
That will not happen if you use EP as it has no Styrene inside.
Additionally, and I am aware that the main reason for you to use epoxy for your specific lay-up might be it's better water
resistance, the following applies.
Mat has a far higher level of crimp than woven materials or uni and bidirectional material.
Imagine it as if you pull on the fibers and they try to stretch before taking the load.
While doing that they loose some of the connection to the resin matrix.
Epoxy has a higher level of elasticity than Polyester and the fibers of woven or multiaxial cloths are already lying in load direction.
You want to use only woven or uni- and/or multidirectional materials with Epoxy. Only that way you fully use its superior properties fully.
Alter the fiber orientation in each layer.
Good luck with the project!