I ride Hixon fairly regularly, I just checked today and was happily surprised to see the flow trails are open. The single track is phenomenal there as well.
Decorah is all old school single track, most of it is excellent. Lots of ups and downs. Plan on feeling lost most of the day as there are 22 miles of wandering trails, fairly poor signage and trail forks is off a bit. The area is ebike friendly, one of the local shops rents and sells a lot.
I'm looking forward to hitting both Levis Mounds and Hixon in the near future - hopefully the spring rains will come on mon-wed so its dry by the weekends...