but as far as antenna types the #XieguG90 ATU seems to restrict options if I understand things correctly; as you said it can’t handle an open-fed multiband doublet.
For trad + WARC a Palomar style 80-10 OCF seems to get me more of what I want than a #GRV5 or #ZS6BKW, even though I’d be looking at ~11-12% feedline loss with the cable I have on hand + 5-10% ATU loss above 20. That seems pretty good? I don’t know.
In any case, this is more fun than studying for the exams.