I live 10 mins from Llandegla and would say it's fine if you are after something straightforward to find and ride. The full loop (including all the black sections) can be done easily under 2 hours.
It'll be a good hour from Chester to get to Betws Y Coed and whilst i've not done the Marin, I have done Penmachno and it is good, but didn't light my world up TBH.
There are also plenty of options to ride up World's End and Llangollen, but you'd ideally need to either find a route/map or get someone to show you round.
Twelve50 bikes in Frodsham (20mins from Chester) have a Weds night ride out I think (usually to Delamere). One Planet Adventure (Llandegla) have a Tues night shop ride (but the next one is a week tomorrow) and Weds night is also BBQ night at Llandegla.
I am going to try and get to Llandegla on Thursday if I can (evening) depending on work, if you wanted someone to show you the way round (not that you can get very lost!).