I don't understand why people think that Morgase could be anything higher than the very lowest level of channeler.
LOC (Prologue) - Fifty times trying to sense the True Source to find it once, and when found, twenty times attempting to open herself up to saidar in order to catch a dribble once.
Morgase is someone who can only sense the source 2% of the times she tries. The one time we saw her channel she was nearly overcome just making a scarf flicker in the wind. I cannot imagine how anyone could be weaker than this. Surely Morgase is a 66! Unless she is higher and the lower levels are reserved for people who sometimes "sense something", but what would the point be of those levels? Or unless she underestimated her own strength, but then the sul'dam thought she was negligible, and basically not even a channeler. According to the quote she can channel 1 in 1000 times!
Sorilea is a functional channeler. She can embrace saidar at will, and do very small things. She's not even comparable to Morgase IMHO.
At least in part. Morgase may well be able to do a few things if she had real dedicated training. At the very least I'd expect that she could eventually learn to embrace the Source regularly, perhaps have tiny effects similar to the scarf flickering, or duplicate simple weaves like Sorilea can. But realistically every time her ability was mentioned it was in the context of how weak she was in the Power, I see no reason to assume she could be anything other than a 66!