I believe TelePresense Server will use the lowest call capacity based on the main video selected when content quality isn't selected, so in this case, I believe it would be 1080p30 (720p15 content). With that said, refer to table 6 of the TelePresence Server Data Sheet to see the maximum call capacity.
MCUs only have video ports when in FullHD mode, refer to Port Matrix in the MCU Series Online Help and MCU 5300 Series Online Help for their maximum call capacity.
Note all TelePresence Server and MCU products are no longer being sold, recommended replacement is Cisco Meeting Server.