Hwy 395 from southern Idaho to Lake of the Woods, Oregon

Why are you asking about just US395? According to the Google Maps suggestion you are spending a lot more time on US20 (Ontario past Burns). After a short length of 395 you are on local (county) roads through Christmas Valley, Silver Lake and on to US97.

Most of these roads are fairly flat, crossing the Oregon 'Outback'. Closer to Lake you start to climb into the southern Cascades. I haven't driven all this route, but what I've seen are fine. Towns are small and far a part. Cell service may limited.