I think I've pinpointed the source of the issue. It seems the Ally really doesn't like Neptastic's resolution upscaling feature. I turned it off and left everything else on including the shadow upscaling (on 2.0) and it holds 50-60fps with 40-50% GPU usage. Looks like I've found what works best here. Thank you guys for helping me all this time. /nepgen/ is better tech support than Microsoft agents.