I thought I should post two things I found that might interest others in regards to Genesis GX Plus.
First thing I found is that you can make the Sega CD games run faster by converting the tracks to .ogg by using isobuster to extract them to wav and then lamexp to convert them to .ogg. This basically makes Genesis Plus GX possible to use for Sega CD games on a New 3DS. I do not know if it helps for Old 3DS. Shining Force CD that ran at 50 fps now runs at around 70-80 fps.
Second thing I found is how to play Mode 1 CD Audio enabled games, so basically Pier Solar with CD audio and some hacks of other games, basically Sonic the Hedgehog 1 with CD audio, Rock N' Roll Racing. I had a hard time finding the documentation for doing this but eventually I found out that for it to work you need to have a cue sheet with reference to the audio tracks, which can be .wav or .ogg. I recommend .ogg for the same reasons as stated before. Track 1 will be the first audio track, not the .bin binary file. Next you need to make sure the .bin executable and the .cue file have the exact same name. To boot the game you need to run the .bin file.
I made a really nice selection of tracks for the Mode 1 Sonic the Hedgehog hack and it works pretty damn good. I can post the .cue file and a list of what tracks I used if anyone is interested, though, I can't share them for obvious reasons. The mode 1 hack I used is called "Sonic1Mode1.zip" and is from 2011 or something. Sadly I don't think MD+ games that work on the MegaSD work. It would be nice to get those CD audio hacks like Streets of Rage 2 or Outrun to work too.
The results are similar to this video, even if it is using a fanmade Sega CD version of Sonic the Hedgehog with features like saving. Plus, I didn't use any Tee Lopes music in my track list since I found some other sweet remakes on SoundCloud and Youtube.
If there's enough interest for this I could make more in depth tutorials on these things.