Have been through in Feb. The first thing I googled was https://yorkcavingclub.org.uk/blog/61-croesor-rhosydd and although it's 10 years old is still fairly accurate. You can do it without any zip line pulleys, as the zip line is optional, but who doesn't enjoy a zip line?
Be warned: the canoe is on the lake and various accounts on the rope/canoe arrangement are mixed, many people say it was fine, personally I found it jammed. Be prepared to swim in worst case (or reverse out again) maybe be more prepared than a pair of Spiderman arm bands which was my "safety kit" for water
There have also been issues with the short "up" rope immediately after canoe where people have pulled it up or cut it down but there are bolts to aid up there in emergency. A large group recently got lost in Rhosydd so read a few different descriptions of that section, but if you've been there before...
If darkness, mist or visibility on exiting is going to be an issue at the time you leave Rhossyd then it's a better bet to leave via adit 9 and walk down to Tanygrisiau. It's a slight challenge going back the other way unless you either know the route well or are good with night navigation.
I did it in January. It is much easier to go down to Tanygrisiau. That said, the weather was horrible and navigating over the top to the Croesor entrance in thick fog and driving rain to start the trip was not easy. You don't need pulleys. The boat system was working fine. Finding your way to the exit adit through Rhosydd isn't always that obvious. There's a lot of up and down in that bit. But all in all, a superb trip.