Hello, as far as I know, it must be Musiccast. See here: https://europe.yamaha.com/files/download/other_assets/8/1245988/web_AV18-0073_RX-Vx85_MCSS_Flyer_multi_B0.pdf I use the MusicCast 20 myself. The setup was a bit fiddly (especially the grouping), but once set up and calibrated it sounds very good to my ears.

Hello, Yes, the signal can be output simultaneously on socket 1+2. Quote from the manual, page 57: "When "HDMI OUT 1+2" is selected, the unit outputs video signals at the highest resolution supported by both TVs (or projectors) connected to the unit. supported by both TVs (or projectors) connected to the unit. (For example, if you connect a 1080p TV to the HDMI OUT 1 jack and a 720p TV to the HDMI OUT 2 jack, the unit will output 720p video signals)" Ahoy!

I have been using the receiver in 5.1 mode for a few months now and am very satisfied with the device! The sound is sensational (depending on the speakers, of course)! I would buy the device again at any time!

The best thing to do is to try Sonos; https://www.digitec.ch/de/brand/sonos-884?q=sonos: You can expand it as much as you like and only need to plug in the power cable. You can then access the system via WLAN with your mobile phone and play music as you like.