I also use an EFHW for SOTA but mine does have a 30m link added (Anderson power poles w/ strain relief). It's nice to have 30m with no tuner for my MTR4B. The K6ARK EFHW kit is appealing, might have to try one someday though my solder skills are not not very advanced and it looks tiny, haha. I purchased my antenna from NY4G.
If you do 2m FM it is nice to use the 818 from a seated position with earbuds by using a ladder line J-pole antenna and enough coax for whatever mast or tree branch you are using.
For phone use with the 818, I never seemed to have much trouble making SSB QSOs with the stock mic and no added speech compressor. Then again, some reviews on the internet say those help a bunch.
Congrats on the DX with low power from Idaho, you guys out West have to work a lot harder than us on the East coast to get EU.
Yesterday bands were challenging. I'm around the house today and hoping to chase a few activators on summits so hopefully the wild QRN and absorption subside.
73