Muirii is one of my all time favourite salvias since I introduced it from seed from NARGS. In our area it grows fairly slowly in comparison to some, so is easily controllable, has small leaves which means it can be hedged or trimmed quickly – you don’t have to worry so much about getting it shaped well – and has pretty blue flowers most of the time.
Muirii is South African and has greyish leaves which indicates it can tolerate drought but is also adaptable to more water and will also tolerate smothering without dropping dead easily, i.e. it will take shade. You won’t have ideal results as in full sun but very reasonable results if you are an experienced gardener