Back in 1996 I did the Michigander which was my first supported tour. I don’t recall the whole route but it followed a lot of the Lake to Lake route. I’ve ridden the Clinton River Trail and Macomb Orchard Trail many times. In fact I just rode almost the whole length of the Macomb Orchard Trail in an out and back yesterday after work for a 50 mile ride. The Macomb Orchard is all paved while the Clinton River is a combination of paved and fine crushed gravel. The 2 actually are connected in Rochester.
I understand the concern about horses on trails. The White Pine Trail between Grand Rapids and Cadillac has sections by Morley that are a bit sandy and they allow horses. This is an Amish area and they use the trail. It can be very difficult to ride depending on how many horses have passed through.