I think in most scenarios you don't need to worry so much about kvm ram use, since it looks static but actually it's not and you can over-commit [1]. And of course disk allocation can be dynamic as well. I prefer a lot more security for a bit less flexibility. I am not as ram rich as you are, and still every time I think of my few LXCs, my main thought is 'why did I do that?'.

[1] https://docs.redhat.com/en/documentation/red_hat_enterprise_...