The stuttering may come from highly populated, overlapping Ground units and fire/ smoke SFX effect.
I’ve encountered horrible FPS drop at NW corner of Hokkaido, many gu sit at same spots, once they enter your view, FPS drop crazily…once your view turn away, FPS smooth.
You’ve to wait dev team fix.
Really true, also because IMHO a general update about this matter should be necessary, considering the higher developing terrains reached.
This mine told, of course, without any will to teach anything to anyone on earth - it’s just my one cent.