I’ve only done it south to north, but think its the best way, there’s a few descents riding s-n that would make miserable climbs the other way.
Tyndrum is a good mid-way point with lots of accomodation, we stayed in the wigwams, but there’s also a hostel (called ‘by-the-way’ i think).
Lots of people will tell you about the horrors to be found on loch lomond side. There is a section after inversnaid which is unrideable and makes for awkward carrying, it can be avoided by taking the ferry to Ardlui then rejoining the way further up the road. We rode/carried it because we were too lazy to organise ferries etc. it wasn’t too bad but took ages.
Run some big tyres and consider tubeless for maximum fun (lots of rocks and waterbars)