Not sure there are any other panniers which fit the standard racks, to be honest, and if you went for removable Givi rack and panniers - you would end up with similar cost, I think.
Shad (who make the BMW ones) have a fairly unintrusive mount system and dont cost the earth for the complete ensemble. There are a couple of threads on this forum on what people have tried. Also - if you trawl through the photo database here - you will get some ideas.
For your pillions - topbox will help, and also “love handles” ( or similar)