Knife is awesome. There are a lot of options around there for fishing and scenery. Up near Cherry and Ottertrack the elevation makes for striking views. Eddy Falls at the end of SAK is a must-see if you get down there. I have heard the Kek Ponds are a blast, with a high chance to see some wildlife like beavers or moose. Knife and NAK/SAK (still Knife) are grand slam lakes and are a great choice for a fishing-focused base camp. The trip into Knife is great and the portages aren't too difficult at all, as well. I highly recommend the Knife area whether you want to go for 4 days or 10 days.
Here is my trip report from my
2018 trip to Cherry.