Hi David. To get to the bottom of this, I deleted com.app.logic.pro.cs along with Logic Remote on iPad to see if this changed anything. I also updated to the latest version of iPadOS.
Surprisingly, I found it was the install of my Komplete Kontrol S61 Mk2 which changed the behavior of the Logic Remote on iPad to automatically open the plug-in window on track selection. This only happens when selecting via iPad, and not through the keyboard or any other control surfaces. Ironically, it doesn't happen when using Logic Remote via my iPhone either. Don't think I can resolve this one and will have to wait for updates from NI or Apple most likely.
Another very odd thing I noticed - the Channel EQ plug-in comes up blank in the Logic Remote. In the mixer view, I can see the curve profile, and even see it moving realtime if changed in Logic directly. If I then open to edit on the iPad, completely blank. All values are 0 and no graph. As noted above, I've re-installed several times with no luck.
As for lag, I was just referring to general moving around randomly selecting tracks, moving faders, opening plug-ins etc. Is ok for the first 10 seconds or so then almost if a buffer overflowed, all subsequent clicks in Logic Pro execute at glacial pace with 2-3 seconds between actions. I have to re-start the app. Tried connecting direct through lightning cable too (vs WiFi), same issue. Perhaps some kind of mis-match between my version of Logic and the iPad remote?