maybe you want to take a look in this thread for my benchmark, btw it’s a fresh qubes.
Mostly that you have big files in there? try run systemd-analyze in dom0, and examine what makes booting take so long.
I’m not sure in my answer, but i do have a appvm that use for qubes-builder, it has 50gb storage space and 10gb ram, i don’t see any difference between the minimal and this vm.