I've been on two trips in the WOWA, once in mid June and once in late July.  Both times there was plenty of solitude.  You'd see an occasional motorized fishing group and an occasional cabin on some lakes, but we never waited at a portage or had trouble finding a campsite.  We didn't go to White Otter Lake but went through the lakes south of their did a circle route thru the Bow lakes and Wasp lake.  Fishing is not as good as Quetico since there is more fishing pressure from the pro's that take a lot of fish out with them.  We're novices, but still enjoyed a few meals of fried fish (that's living!).