I did this route in August 2007 in the direction you are going. There will be some low water on Baptism but if it's dry enough to cause dragging in the creek then the long portage to Cache lake will also be dry and much easier than during a wet season. Enjoy the hike.

Tricky part is finding the Baptism where it flows into French River. In 2007 there was a small piece of flagging tape marking the mostly hidden confluence. Ask about it at park HQ when you pick up your permit. They will give you fresh intel.

The portages along the river are not what I would call easy but if it's dry in August then they will be as easy as they get. Mostly they are easy to find and follow. Some have more of that flagging tape to mark the route.

Solo, I made it from the campground on French Lake to Cache Lake in 7 hours. You will know you did something when you are done.

Welcome to QJ