The GO Aps do perform auto-channel and frequency. @Mouxy That being said, it is always worth doing a quick scan and reviewing the channel best for you, and manually assigning them to your access points.
You can change radio settings on a per access point basis in the app under the Hardware view.
I was doing an un-related investigation on my GS110 48 port switch and found that they do indeed support IGMP. There are membership reports and queries behaving as expected during some testing so I thought I would come back here and set the record straight.
This means that multicast traffic only reaches ports where members have requested to join the IGMP group, but if a group is not known the multicast traffic should still be flooded.
If you need this changed or feel you are facing an issue with IGMP, please do not hesitate to reach out to support for assistance.