Speak to your installer and specify motorised. If after this he is pushing you to go fixed multi-LNb route, I would find another installer. Chances are he won't be able to set up the fixed dish either
If you do go fixed with Multi LNb arrangement, The Triax 20 deg Triax bracket will be fine for the four satellites you mentioned. I would say align on 19e prime and offset 13e, 23e & 28e