I played 2 tables on HUSNGs generally (turbos and regular speeds).
I played 2-4 (sometimes a few more if vs the same person) when I played hyper turbos regularly too.
It's generally easier to multi table hypers because you're at closer effective stack sizes in all tables. When you're playing turbos, and you're at 75bb on one table early on in a game, and 40bb on another, and 15bb on yet another, it's a lot more confusing and takes more time to move from table to table. On hypers, you're always at 8-25bb where you're minraising, limping or folding preflop on the button (and lower than 8bb is easier).
If you're having trouble learning to multi table HUSNGs, I find it easier to add tables by playing a few buyins lower than your usual stakes, making sure you have no distractions in the room, and by trying to play against the same person on some of those tables.