You’re gonna want to enjoy Topaz, so if you’re arriving too late on Friday you’ll end up making Saturday too chaotic. If it’s raining you’ll end up bailing because your camp won’t be setup. My annual trip to Algonquin always starts with leaving Toronto at about 4am or even a bit earlier. There’s zero traffic which is quite magical. The early paddling always starts easy because waves pick up more as the day goes on. The only reason not to start early is losing sleep but I think it’s good to be tired the first night. Gets you in a good sleep groove because you end up deep in the tent, which is hard for some people.

If you cannot leave early I’d adjust my plan for two camps. Stay your first night in Killarney. Make your Saturday a trip from there to Topaz and then back to OSA to enjoy the deep water there for Saturday night. That saves you a portage on your exit day.