I am not that good at mixing but the rule of thumb is, I guess, to put low frequency instruments in center. Higher frequency instruments can be panned. Low cut on almost anything except bass and kickdrum. I use Izotope as well but can't let it control everything, it ends up in a harsh result Their loudness control, maximizer is great. It would be fun to try mixing your stuff if you like but I am sure there are people here who are a lot more competent.