I have cae "chinese alge eater" hes doing ok but i have seen the damage they can do by sucking at the slime coats of other tropical fish not sure if this is a problem with cichlids if mine tried it it would be only once.
Bristlenose plecos seem to be the most popular plec for mbuna tanks. They are small enough to not take over the tank, and seem to specialize in ignoring even the most inquisitive cichlid.
Yep, BN Plecs should be fine as will most of the Synodontis Catfish species. Another option would be Pim Pictus, which are often kept with Mbuna and can cope with the aggressive behaviour.
yep perfect , I forgot about the b/n its without doubt the best alge eater there is ,I think the pim pictus needs a more meaty diet so may not be a suitable as the synos.