Little Manistee, Lincoln Hills, & Tin Cup are the main ORV trails in the Manistee side
. I'm assuming you're referring to the Manistee half
(west side of the state) of the Manistee-Huron Forests? It can be tricky with all the private land mixed in with the forests there, but if you can use a mapping software
(gaia, etc) to see the distinction between public/private then you'll find there's a ton of trails to wander in that area. It's mostly easy going tracks, usually only gets difficult in the lower lying areas during heavy rain/snow. Anywhere you see the trails nearing the rivers & bodies of water can make for good camp sites. Use the "terrain view" in any of the mapping software's to find more interesting spots, & even just using google maps for that + satellite view allows you to do a fair bit of recon ahead of time for route planning. In my experience there isn't much for "big sights" to see out there, aside from maybe the Udell lookout tower or the dunes where the forest land reaches out to the Lake Michigan coast in the northern-western section of the area.
Maps:
http://midnr.maps.arcgis.com/apps/webappviewer/index.html?id=1710727ba3ec4c64928110fdb4f7799d