Pragel pass from Klöntalersee to the Passhöhe is closed to non-locals on weekends. The climb from Glarus is pretty narrow and gets busy so a very early start would be the most relaxing - or take the Postbus up to Klöntalersee.
Same weekend setup with Grosse Scheidegg from (probably about) Gletscherschlucht Rosenlaui - same deal with a Postbus option to avoid the busy section.
And Stein to Amden is a forestry road - corrugated concrete so better to climb on than descend. I've never seen a car on the weekends.
That means, generally, along waters, like the Vineyard trail. Alternatively, you could start at an elevated location as that will enable you to enjoy going downwards, like the Rhône Route from the Obergoms all the way to the Léman (pretty flat after Brig).
Komoot is worth it. You can find all kind of vouchers on the internet for the maps but I ended up buying the whole pack. I did this route created with komoot last Sunday and I must say because I am able to choose where I ride, there was not much traffic. I started at 11.00 AM and it was great. But during the week especially if you ride in Zurich it can be at times dangerous.
To be honest I do not mind so much the distance...I have never been almost killed because of it it is the drivers not knowing or not respecting the rules. Honestly a driver told me in traffic that a bike has not rights on the street
In town/city where cars are going 30-40kph, most cyclist will not mind too much the distance. But on a 80kph road, its a different story. Most drivers will give enough space but in my experience there is always that 1 (or 2) idiot who will pass with a car in the opposite lane.
Greifensee is a great option but not on weekends...way too much traffic...Saturday and Sunday until noon is ok but afterwards is full with rollers and too many bikes...if you do not have a roadbike and do not mind traffic...then go.
Along the Töss is also great with not so much traffic like Greifensee and completely flat.
Sunday morning before the drivers wake up the Lake of Zurich is also a great option and you have a bike lane...and almost flat
I never felt in danger cycling on a regular road per-se, but recently I switched from mountain bike to road bike and it's a hell of a difference. Now I ride much faster but my stopping distance is much longer. The thin tires can't hold the bike, they skid easily. To make things even worse, because of the leaned forward position I miss the road signs sometimes as they are out of my field of view, they are mounted too high. But I like road riding, quite a new experience!
So well, if you are afraid of cycling on regular roads, maybe start with mountain bike on fat tires
I am also a fan of flat / lazy-boy cycling, and also prefer not to share my tarmac with cars
I had a really nice cycle along the shore of Lake Constance / Bodensee earlier this year. There the cycle path is 99% away from roads - there were a couple of times when you have to cycle on a road for 200 metres or so, but that's on a quiet road, so not a big problem
I cycled from Arbon to Kesswil
It was lovely, although by the time I got back to the hotel, I felt very saddle-sore - I was so happy to "dismount"
The train is usually a useful alternative along the lakeshore as there's a stop every few km. Usually ships are available, though perhaps not while you were here due to the high water level. If you're a bit away from the lake there's usually a bus more or less nearby that will get you back (unfortunately you may need to have time to spare).
If you are searching for flat smooth roads with few or no cars I would highly recommend riding along the Reuss river with many nice sections from Bremgarten heading south with beautiful views of the mountains on a clear day.