I made a 4-day hiking on Western Uplands Trail in Algonquin Provincial Park, from Rain Lake access.

Day 1: Rain Lake to Ishkuday Lake (9 km)
Day 2: Ishkuday Lake to Pincher Lake South (14 km)
Day 3: Pincher to Brown Lake (11 km)
Day 4: Brown Lake to Rain Lake acess (13 km)

Especially Brown lake was beautiful, and it made whole the trip rewarding.

4 Day itinerary might be a little bit redundant. 3 Days would be good if you can get the right campsites to stay.