I have only done 1 BOM, it had no group, but I would imagine the LQS that I purchased it through would have been a resource had I needed help. I found the cost very very expensive 28.00 per month for 12 months and the fabric was cut with no room for error! After that I only buy a BOM if they offer it as a entire kit, or I will purchase the pattern and find my own fabrics. I don’t do Facebook or other Social Media as it’s not my cup of tea. I think like any group, you will find the range of participants to be from beginners to expert and you may or may not get anything out of it depending on your own quilting skillset.
On the other hand, I find the Annual Bonnie Hunter Mystery QAL’s here to be very helpful and inspirational.