Are you looking for just spots to overnight while traveling or to set up a Kamp here or there for a time?
I-75 from the Ohio border north is basically nothing but “Detroit megapolis” or farmland until you get north of Saginaw. Once you hit the Huron National Forest land you can Kamp about any place you want on National Forest property.
If your not in a hurry I would suggest leaving I75 at Standish & drive US23 along the Lake Huron coast to the bridge.
Once in in the Upper Peninsula, US2 is the southern route and your blue line shows you leaving US 2 around Blaney north toward Senney to take the more northerly route on 28 & 41 . As far as camping in the UP; you can practically pull off and Kamp wherever you want as most of the UP is National or State Forest property.
(I’m in the “Beach Bums” area, sayin)
Again; I don’t know if you are taking your time or just looking for night spots while driving straight thru.
intjonny