If you're renting an EV for this trip, it's Tesla all the way. I wouldn't bother with anything else, in particular because Tesla's SuperCharger network is head and shoulders beyond other providers in terms of availability and uptime.
Follow Out of Spec Motoring on YouTube. Specific videos to watch are the road trip ones, where the host visits various rapid chargers and highlights the quirks of each one. He does a great job of wringing out the most drive time v.s. charging time out of every EV.
As for destinations along your way:
- Duluth is a really cool town and worth a visit on its own. Take a run up Hwy 61 to Grand Marais if you have time, right along the Lake Superior shoreline. Simply spectacular views!
- In Mitchell, SD, the Corn Palace is worth seeing, but the Dakota Discovery Museum is a better reason to stop.
- I wish I had stopped at the Chamberlain (SD) rest area on I-90 just before the Missouri River; it's a gorgeous sight after many miles of farmland.
- Wall Drug is overrated. Maybe it's better if you show up more than 30 minutes before closing. But I'd rather spend more time in the Badlands instead.
- Badlands NP and Crazy Horse were definite winners. Unfortunately Wind Cave NP and Jewel Cave NM were closed when I went. Hard to go wrong with spending more time in the Black Hills regardless. Everyone knows Mount Rushmore, but that's the least interesting reason to visit.
- Definitely do the Beartooth Highway; it's really close to Billings. It is utterly stunning. A caution - the later into September you arrive, the more likely the Beartooth will have closures due to snowfall. In my case, I made it from Red Lodge to the Wyoming line, then was turned around.
- If you don't end up taking the Beartooth all the way into Yellowstone NP, circle back up the Chief Joseph Scenic Byway (WY-296). I think it's just as stunning.