Oscar, RD/midas, chocolate, mota, Viejas rarely get above 12". Yes some do, but the majority will max out at a foot in length. Most of the time those fish would be fine in the 110, but if you were to get the uncommonly large specimen, I do think it would be better off in a 150+. The jaguar, black nasty, and snook, all should have a larger tank. You could keep one for a long time in a 125, maybe for life if it doesn't grow to potential, but it would be better off in a larger tank. As we are giving somebody with an empty tank advice on what new fish to get, it doesn't make sense to me to tell them to get a fish that would just barely be "okay", when there are plenty of fish that would do much better and thrive in this smaller tank. The equivalent of a buttikoferi in this 110 would be an RD/Midas/Oscar etc in a 55 gallon tank. Will the fish die because the tank is too small? No. But are there plenty of much better options for the tank size? absolutely.
Wait so you are trying to tell me that a Jaguar or Snook would bearly fit in a 125 gallon tank that is 6 feet long and 18 inches wide?
I have had Red Devils reach 14 inches, Viejas rarely get 12 inches? Really are you sure about that, my Synspilium is 15+ inches.
I get it a bigger tank is better, I don't argue with that. But according to your logic it would be like me telling someone that a 30 gallon tank is too small for a Amp. Brichardi because the width has to be 2-3 times the size of the fish, a bit overkill IMO.
Like I stated before if the industry went by you and Snazz's logic then keeping fish in a glass cage would be illegal.