Sorry, I see in your email you wrote 60-100km.

Three suggestions for you:

1) Senya and Kvaløya: A beautiful loop with plenty of places to wild camp and fish. You can explore some of the dead-end roads on Senja (leading to small fishing villages) if you want to add extra km.

https://ridewithgps.com/routes/43186780?privacy_code=2C5LRdSSjHaMnwPc

2) Lyngen Alps: Another stunning area with plenty of fishing opportunities. You have a small section on the main road E6 but if you time it correctly it should be reasonably quiet and not a concern to cycle.

https://ridewithgps.com/routes/42506798

3) Cycle down to Lofoten: This is about 400km (including ferry journeys). Finish in Svolvær and then take the Hurtigruten back to Tromsø. This may be a bit rushed as you will need to work out which boat to catch to reach the airport on time.

http://www.cyclenorway.com/routes/atlantic-coast-route/overview/route-3/bodo-tromso/

https://ridewithgps.com/routes/39301335?privacy_code=STxgwydAwbrhUcGk

You also have some other options here for a day or overnight trips from Tromsø: https://cyclenorway.com/routes/base-days-rides/overview/route-9/

Personally I would cycle number one as I think it ticks all the boxes for you and is comfortable doing in the time frame you have.
I hope this helps!