Not sure if this useful but I’ve just timed my Late 2013 iMac (SSD) and it took 20 secs to login and then a further 3 secs to desktop, I don’t have any login items (ie. programs set to run on login).
From memory I believe High Sierra would get to login in about 15 secs, strangely I’ve noticed since Mojave there is a distinct pause half way through the 20 secs as though the system is doing some sort of check, never noticed that on previous versions (plus the pause feels like the “missing” 5 secs).
Saying all that, it doesn’t really matter since I usually sleep the iMac anyway, and waking from sleep seems the same as previous OS’s.