Personally, I like using Lancers for training mags. First, they come in purple, which is both easy to see on the ground and easy to differentiate from everyone else’s, and second because I am not 100 percent convinced of the two piece design. Having said that, I have yet to have an issue, including full auto suppressed.
For work purposes I use the latest gen windowed Pmags for my barrier blind rounds, and Okay or DH for green tip/penetrator rounds. This allows me to instantly ID by touch what I am loading.
I do use some 20 round Pmags on my low profile kit. I have had no issues with the slightly curved mags, but honestly the straight profile mags worked fine for me as well.