Stocking Idea?

Angelfish can work if you diffuse the current of the filters.  

The pleco can work, without the giant hoplar, a lot of other things could work, though I would consider fish that are not giants, and not cichlids.  The Rest of the tankmates should be peaceful, non-nippy, non-territorial, Not bigger than the Angels.The hoplar  gets to 18 inches and that's too big for any of the 48 inch long aquariums, maybe if you had the next size, a 72 inch long aquarium.

Hoplarchus psittacus get quite large and cannot be kept in a 75 gallon. 

The biggest problem would be the Angelfish as they are not strong swimmers and the filtration for a tank that size the filtration may just suck them in. I run a 75 as well, along with Two Emperor 400's. Angels would Never survive in there. 

I would recommend using the thinkfish.co.uk Community creator. It's super easy to use you just have to put in your tank measurements and what type of filter your using, it'll tell you if the fish aren't compatible for your tank or each other.