In the case of the NooElec balun, just know that there is a single copper trace on the back, which you can scratch through to make it galvanically, aka a physically isolated transformer, which can help to keep common-mode coax braid from being part of your antenna system.
The R75 also has a built-in 10:1 transformer which you can switch to. Normally this is used for high-impedance feedlines like 300-600 ohm twinlead. OR, end-fed wires.
Normally most don't use it because of the indoor noise problem, but you can also try this little trick on some bands with your existing setup:
Disconnect the coax cable from the back of the R75. Run a small jumper from the high-impedance push-in jack to the center conductor, maybe with a little alligator clip jumper, make the antenna switch in the R75, and see if it improves or degrades your reception depending on frequency.
Don't forget to switch the R75 back to the coax antenna when you screw the coax back in for use in that mode.
These are just general purpose notes, since we don't know how bad noise is at your location. It's a simple thing to try however just for fun.