While I do not find tetra to be huge problem with fin nipping, they can be a bit of problem with angels as they tend to swim under and around the angels and that does often give the angel a nervous feeling which I do not like to see. Often not a real big problem but with the hundreds of great fish to combine, I tend to go with better choices when I can.
Pleco can also fall into the same group when dealing with plants as they do often like to "rasp" on organics and that may mean some damage to plant leaves. Some work okay, some don't, so I no longer keep them in my normal planted tank as it works fine without them! I tend to look for the "low worry" solutions, so look at various algae eaters as a better choice. If I really, really, felt the need for pleco, I might but just not true for me.
Lots of really nice small safe cichlids which work well in 75. Some I like are neets, curvicepts, and those types who do stay small. I do stay pretty much away from the big bully type cichlids in my planted tanks as they are too much trouble but cichlids like the angels and the small folks do work well. Too many folks have tried cichlids like oscars, dempsey, etc. and just never looked further.
Clown loaches for a pair to show lots of color and action without much trouble might fit very nicely in a 75? They may get too big 5-6 years from now but then how long do most of our tanks remain the same for that long?