There's some very good river trail info on the MN DNR site. Here's a interactive map that shows accesses, camp sites, etc. https://www.dnr.state.mn.us/watertrails/interactive_map/index.html https://www.dnr.state.mn.us/watertrails/index.html
Both the Upper Mississippi and Rum rivers are excellent for SM. But, their scenery is not that of the northwoods and the Arrowhead areas. It is more rolling and agriculture in nature. The North Shore is beautiful but I believe it to be more trout country than SM.
Other suggestions to check out are the Root and Zumbro rivers in SE MN. This area is Mississippi River bluff country and it is beautiful but in a very different way than the northwoods. The terrain can be rugged, especially closer to the Miss River and it's more of an ag/mature forest mix vs the northwoods which are more pine forest. Feeders to these rivers are most likely trout streams but the rivers themselves are warmer and very good for SM. I wish I could be more specific in recommendations but I have spent very little time stream fishing. There's just too many lakes to explore.
Over the years, I have found the folks at the DNR Fisheries Offices to be extremely helpful and a call to one or more of them would be well worth your time. https://www.dnr.state.mn.us/areas/fisheries/index.html
For the SE MN rivers, I'd contact the Lanesboro office. For the Rum and Upper Miss, the Little Falls office.
I should add that for most, if not all of these rivers, if they've got SM then they more than likely have Walleye.