[added my measurements]
I’m using the performance governor (as hinted by @renehoj in this post) with 6 dom0 vcpus, pinned to E cores. Using the ‘ondemand’ governor is a tad slower (+0.5sec).
5.6s startup time is great compared to my old T450s that’s been running qubes for the past 7 years, but it’s 50+% more than @renehoj (which I assume ran the test on an MSI Z690-A Pro DDR4 - same as mine). I doubt it’s only down to the CPU (i9 12th gen vs i5 13th gen), it might be that btrfs also gives an edge with lvm operations when starting the vm.
[edit: forgot to add that disabling memory balancing as per @augsch 's advice shelves ~0.5s; total=5.1s]