Ive ridden all of these trails, here are some blog posts about them from last summer with photos, maps and reviews.
'4 Trails Area' (Great River, LaCrosse River, Elroy-Sparta, Great River) -
http://bartsbiking.com/?page_id=65
Glacial Drumlin -
http://bartsbiking.com/?page_id=61
I personally ride on a Trek 7.5 fx hybrid with 32mm tires and find this perfect for these trails. The '4 Trails' are all dry, limestone trails, not paved and move relatively fast. The Glacial Drumlin is the same, but last season was not in as good a shape as the '4 Trails' The only paved part of the Glacial Drumlin trail is from Dousman to Waukesha.
Ive talked to people on road bikes with 28mm tires and they are fine for these trails once they are groomed (usually sometime between mid April and May)
The Great River trail is a wonderful site and i cant wait to get back there this summer, if you have any other questions let me know.