oh, if that is reason, I'm totally fine with it. I like lower power consumption( only if the max performance is the same as before).
Just like @Jorge Teixeira, the memory integrity setting was already disabled for me.I resolved it by disabling memory integrity in windows security, is it enabled in your case?
https://forum.proxmox.com/threads/windows-guest-slow-after-pve-6-to-7-upgrade.93302/#post-435442