I use MG with GarageBand via a Scarlett 2i2. I don’t use it a lot, and I have had very mixed results, some good but mostly bad and I can’t achieve a stable state where it works the same every time. I use two acoustic guitars;1. Martin GPCPA4 with Fishman F1 Analog electrics. 2. Santa Cruz VJ with an LR Baggs Anthem SL dual mic and piezo pickup. I have these problems with both guitars. Either there are too many “ghost notes” or if I manage to get rid of most of those I cannot get much output at all. Add to this a strange phenomenon of voice activated notes! I can play the thing just by talking or singing! I need help to set the system up. There are too many variables for a simple soul like me! Help!
Somehow there must be a mic that pick up ambient sounds, like talking. Thats not really going to work.
Are you sure its not using the built in mic of your MacBook or iPad? Use pickups rather than mics. As longs as you get a clean and reasonably loud signal out of your pickups it should track even at a very low noise gate.
Using acoustic guitars will not work as well as a solid body electric guitar, in general, but this sound like a you have more issues than that.