u/Caprapas

Hey everybody, I am planning to make some knights for Greathelm with my gf, and I was considering getting a couple of boxes from different manufacturers to mix and match, but I don't know if the sizes will be compatible.

I was thinking of using some Perry miniatures as a main base, either from their early 15th century or late 15th century kits, and adding to them some Victrix miniatures and Frostgrave pieces. Are these three systems compatible with each other? Also, does anybody know of any other manufacturers of minis that are more or less historically accurate and compatible with this size? I know Frostgrave isn't really historically accurate, but you could get some interesting heads from it!