For single seaters use either 30° or maybe the 25° if it is still available. Depends a bit on your size / seating position.
Quick release tethers are a bit a waste of money, as usually drivers take the Hans and helmet off at the same time.
But if you like them, feel free to buy them, us retailers will be happy.
Bell will only place the clips at their HQ, but will not drill holes in a helmet. Most other brands allow some of their dealers to do the work (never drilling).