I have never been on one BUT---if time off problem they are fine, they make all the plans for you and have bike to rent. I lived in Europe for 20 years and have ridden most of the stuff they cover. I would expect skill levels of groups to be varied---mixed groups, American level of skill and ability to twist throttle probably less and fear to ride the mountains right.
Riding, even in small groups, at best dangerous.
Time/money not problem, ship/fly your bike, take 3 months camping and really enjoy----my estiimate total cost would be about same.
Would SilverWing work on solo trip=sure. If your reg motorcycle skills are not high, rented BMW, etc could be nightmare for you on organized tour.
I like Norway/Sweden early summer, Sept Germany and Switzerland. Iife much more enjoyable once your figure it out. Rally I really like Stella Alpina (Brits tried it?) ----but you won't see Fat Bill and big Mona on GoldWing going up ---to get pin/tee shirt required about 30 km up mountain in mud/dirt/sometimes snow---did it on Vespa 150(perfect), R80RT-knocked fins off crankcase/bent exhaust crossover--MZ 250 just putted up and down. Have fun.