Also for a centre, do u just rotate a normal wall speaker 90 degrees? they only seem to have upright wall speakers.
You can, but the centre speaker is actually really important for home theatre. That's where the dialogue normally comes from and it's usually very important that you can hear what people are saying clearly. The centre speaker is usually optimised for the human voice frequency band. I think you either get a good centre or opt for the floating/phantom centre channel, where you don't have one at all, instead relying on the side speakers to generate the centre sounds as well.
So, me, I'd go for a real centre speaker, be that wall mounted or other.