i doubt a senegal can swallow a raphael but the rasporas and platies will be food for sure.
for the tank size definitely a senegal. get the albino one and put black gravel. any fish that cant fit in its mouth should be ok (large gouramis, angelfish, etc)
As for people who says plecos and bichirs are not a good idea. I have yet to find this a problem. It's been over 8 months and these guys are fine together. My highfin pleco and bichirs do not bother each other.
nope^ Ill just go pick up a 40breeder, I just found out im getting a 120+ so I will keep them in the 55 or move them to the 40 and do some cichlids, dunno yet.