Logic Pro for iPad 1.0 forces the Mela plug-in to fully redraw at a high refresh rate when the user is resizing the plug-in window. In some cases this makes the window resizing very laggy. No other DAW is causing this sort of an issue either on macOS or iOS.

Hopefully, future updates of Logic Pro can address this issue. But in the meantime, I will also be investigating what I can do on my side to reduce the lag.