Gene,

See my trip report for details on the Cache Portages.  McKenzie to Cache is definitely harder than Cache to Trousers.  There will be plenty of mudholes.  The African Queen section was the only place where the trail was hard to pick out.  It's a maze of channels in there and it's best to scout the way thru before you start trying to carry stuff.  When we hit that section, we loaded the packs back in the canoe and walked the edges of the channels while pushing the canoe along.

I didn't get a lot of time to fish McKenzie, but there are lakers around the pictograph areas.  The wide-open north section seems  much shallower but I wasn't running a depth sounder so I can't be sure.  

Didn't really look for campsites in the north end of McKenzie so I'm not sure what you might find.