Annecy to Chamonix

You can check yourself on Google maps

It’s about a 1 hour drive each way, bus will take longer

That's the total time on the bus, so, basically, round-trip.

WE did this right as things were opening up after COVID -- the bus trip was a bit more than an hour each way.
https://janettravels.wordpress.com/2023/03/27/quick-trip-up-the-aiquille-du-midi-chamonix/
When we did it, most routes were still cancelled and the one that got us to Chamonix at 11 or so and then left to go back at 3 was our only choice -- it was fine -- but you probably have more choices now. Note that while BlaBlaBus was fine that not all their buses were labeled. We almost missed the bus back. Going it was giant and orange with BlaBla on the side. For the return it was a plain white bus without so much as a destination card in the window. If I hadn't asked the driver, I would not have known it was our bus.

That is very helpful, especially about the markings on the bus, I wouldn’t have known that - thanks.

We were sitting on steps across from the bus area looking for the big orange BlaBla and it was pure luck that when we didn't see it i walked over to the plain white unmarked bus. The driver had our names on the list and seemed surprised I was asking like 'anyone out to know that a totally unmarked bus is the right bus, duh?' We came close to having to take a very long train ride with many transfers to get back as we were leaving Annecy the next morning.