The Alpine passes are amazing, have done so many I couldn’t list them. Do some internet research as some of the best aren’t the most famous or obvious in a road atlas.
The most amazing I have done is the Großhochalpenstrasse in Austria, absolutely amazing views.
Stelvio is a monster, it’s pretty tiring just driving it with all those hairpins - I couldnt believe how many looneys were riding up.
All the directions out of Andermatt are spectacular, the Furka, Grimsel, Susten loop being brilliant driving entertainment, and the Nufenen has huge empty mountain views (and don’t forget to stop on the Furka to walk the tunnel inside the glacier!)
Wasn’t that big a fan of the French passes but the Col de la Bonette is stunningly remote, and very very high and precipitous (then you find that some poor soldiers had to man fortresses up there!)
It’s really hard to plan trips, as ideally you need to follow the good weather (not a lot of point being up there in the clouds and rain) and hard to judge timings. The passes are actually quite short so you can cover a load of them in a day, but you can’t judge purely on mileage as it’s highly dependent on how many times you just have to stop and take photos (it will be a lot!).
If you enjoy driving and can afford it driving round the Alps is an absolute must, I couldn’t recommend it more - I would have done even more if blooming France didn’t make it such a long drive out there (though still possible in a day from the South East). Go in September, before the winter tyre regs in October, but after the schools have gone back - the roads are pretty empty and if your budget isn’t too tight you can use Hotels.com/Booking.com to find hotels as late as that afternoon so you can be really flexible where you go.