By the way, before I changed my modem to Bridge mode, I did use the app as well as the web page to make changes. I found the same limitations to changing things like channel and mode with the app as I did on the web config page. My understanding is that Comcast doesn't allow access to some settings on rented modems. If you purchased your own modem (instead of renting theirs) then you should have full access.
THANKS ATC-- I'll look into getting my own modem and get bvackif I need further assistance. MUCH appreciated.