For your original question: as you're a EuroBonus member, I'd choose Lufty, as you can earn some points and transferring at FRA is just as painful as at AMS, imho, although it probably is completely different than usual.
I've done some international traveling during the COVID-lockdown, in fact to Norway. As I'm not a Norwegian citizen, but a PR there, I can share my experiences, as the rules for Norway and Canada are very similar. I don't think they'll refuse you entry, as you have a very good reason to travel to Canada. The point of stricter controls is in fact to keep people out who have no business there, not to make it impossible for people to get back home again to their beloved ones.
First, put the face mask on and keep the darn thing on the whole time, on board and after deplaning. The chance of getting infected or infecting at the terminal is in fact bigger than on board, up in the air, when the ventilation system is on. This is also mandatory, it seems, for Canada, while in Norway most face masks disappeared at the exit of the aircraft and aren't put on just before boarding... Keep it on and avoid any issues there.
I got greeted by military personnel at Arrivals and had to prove that I both am a PR in Norway and that I had a 'plan' for the first two weeks. If you have a certificate or stamp in your passport or so showing your status, then bring it and show it. If you have a Canadian cell phone number, driver's license or home address then make sure you mention it or show it explicitly at the control point, for example by filling out this information on any immigration form that you may get your hands on. If you have the opportunity to write a few sentences and print it on a sheet of paper, that may help. I hadn't had the chance to do this, as the rules got changes while I was traveling home, but I got in nonetheless. I could show a Norwegian driver's license, I speak Norwegian fluently and I have a Norwegian cell phone, so that was more than enough to convince anyone.
Make sure that you're being picked up at the airport and make sure that the person who picks you up has their cell phone readily available in case they want to check. I offered staff to do so, which convinced them more than enough to not deem that necessary. And most of all, look convincing, act convincing, have no doubts. Which should come naturally if you actually prepare the trip properly. So I wouldn't be too worried.
One tip that's not about rules and regulations: have enough to do. You won't realize how long two weeks of quarantine in a house is until you're experiencing it. And make sure you keep on moving and exercising a bit. I gained a few kilos and got out of shape.
Anyway, masse lykke til og god tur!
ps. I was on Gardermoen 3 days ago for a domestic trip. Please know that the International part of Gardermoen (airside) is closed until just before departure. Even tax free may be closed, just like all other shops there.So if you need some food or drinks, get it at the domestic part. Also, all premium lounges are closed.