I rode the Srath Beag/An Slugan route as part of the Sligahan loop in March last year.
I rode it in the direction Torrin to Luib. I say “rode it” but alot of it was hike a bike (at least for someone of my abilities anyway). For me crossing this glen came at the end of the ride (i started and finished in Luib) and to be honest i found it a bit of a slog in places. This wasn’t helped by it being a muddy time of year.
It would ride much better, however, in the direction Luib to Torrin in my opinion. This would leave you descending the pictured singletrack above 8) The climb from Luib would be a bit of a grind which would be “hike a bike” for a reasonable portion.
I can’t comment on how it compares to Srath Mor though as I have never ridden through that glen.
Take the dotted path towards Strolamas (the old road) which will get you off the main road (you can also avoid another main road section by going round the Moll road near Sconser).
The section through An Slugan uphill beside the stream would be mainly hike a bike to the highest point then it would be mainly rideable through Srath Beag down to Loch Slapin.