The P seems simple enough, and it really is, pretty much.
P usually has a bigger bowl than R, because it has no leg occupying the bottom negative space.
The higher the waist of P, the more awkward it will appear next to letters like T and V that have large areas of negative spaceon the bottom left.
Because we have plenty of room for it, the bottom right serif on P can get pretty big.
Using both of these moves to extreme degrees makes for funky looking Ps, but they space much easier.
The lowercase p looks so similar to the uppercase, but the key differentiation is the way the bowl connects.
The bowl of p is vertically symmetrical in expansion, but translation shows a big difference top to bottom.
On occasion in translation italic designs, we get to see this cool form of p with the stem overshooting the x-height, and an entry stroke leading into the bowl.
And in expansion italic, we sometimes see this lovely form that also features the overshooting stem. P and p are not so stale after all. ✌