Elysium is definitely the slowest, but time saved carries over, so if you’re fast on Tartarus, you’ll have more time in Asphodel, which is relatively short in terms of number of rooms, and subsequently more time in Elysium.
And as someone else mentioned, it saves time to be aggressive too, so never be idle and try to anticipate where enemies spawn. Enemies without shield (or when the shield is gone) can be stun-locked, so just hammer away at them.
Maybe I’m forgetting how much time and practice I’ve put into going faster, but if I can do it — everyone can, that’s for certain.
Drawing inspiration from speedrun builds is great, so maybe check some of those (linked earlier) out. There are builds for different play styles, so I’m sure you’ll find something that works for you. :)