I'm glad it was helpful to you both. David, I hope you have a wonderful trip and that you'll report back here how it went!
Sergey, keeping in mind that I only did a short portion of the Kopka (from Hook Lake to Bukamega Lake), I did not need to paddle any whitewater. In higher water, maybe one of the rapids would have been runnable, but I lined it, and there was a portage option.
In his Wabakimi Canoe Routes Guidebook available on the FOW website, Laurence Mills has a pretty long and detailed summary of the trip. I'd suggest looking there and/or talking to outfitters or other folks who know the trip better than I. There's also a nice video from "Explore the Backcountry" that might give you some idea of what to expect: https://youtu.be/CEqvmDgrAA0. That pair seem to really like running whitewater and makes some really watchable videos.
I had some self-inflicted problems on a put-in, and struggled to find one portage (that may or may not have been there). Make no mistake, some of the portages are quite challenging, and some of the put-in's take-outs were a little challenging due to the low water, but I suspect higher water would just change which were easy and which were more challenging. However, on balance, I didn't find the actual put-ins/take-outs to be particularly remarkable or problematic.
In case it's of interest, I did a webinar with FOW a few weeks ago that also covers this trip. You can watch it here: https://youtu.be/8koQ88x_jfs
Good luck to you both wherever you may go!
Cheers!
Rob