I agree with Alex. The peony will need more space to grow. Unfortunately, the foundation is too close. There are a couple of issues with this. Rainfall is one of them. The area close to the foundation will probably never receive enough rain. Furthermore, the foundation may be porous and absorb water taking it from the peony.
As per the depth, I really cannot tell without seeing the grafting point, which is supposed to be good 4-6 inches below the soil level:
https://graefswinning.be/en/co...
I've happily planted up to the third level of leaf branches, which is about two times deeper that recommended above. It is very cold overhere and I wanted to be on the safe side and protect the scion. The idea is to enable the TP roots to develop from the grafted TP branches. You are lucky that your TP has three branches. For example, if something happens to one the branches, the other two can continue growing roots.
