Unusual scenario

I know we technically are not supposed to have two modems but i swapped my plan after being convinced to do so (kind of wish i hadn't) anyway that's another topic, i got the new plan and with it they sent me another modem, it is the exact same model i had already, but its much faster (500-800mbps) than the old one (200-400mbps), but the old one provides landline phone service, and connections for the front of the house and many many devices, i was supposed to swap the old one out for the new one, but it wont provide landline service for some reason and techs couldn't really figure it out, so they told me to just keep them both if that works for us, even though they send me emails almost daily asking me to return one of the devices, one of the issues is i cant separately access the modems login pages, and it shows many devices as connected via moca, it seems maybe the second modem is acting as a moca adapter somehow? i dont have a single moca adapter yet there are around a dozen moca connection, to devices that are for sure connected via wifi, so i know i need to turn off dhcp on one and set a static address on the second and it was suggested maybe to turn bridge mode on but i need both of the modems to connect to internet via coax and provide wifi signal, but it sounds like that's not what it does in bridge mode. also another issue is the new motion detection via wifi doesn't seem to work with the new router at all, and i cant watch live tv on computers/tablets as it says i am out of home. also often my internet connection on my pc says no connection often (assuming dhcp issue?) and my ps4 basically wont connect at all even with an ethernet connection and xfinity blocks you from changing a bunch of advanced settings that used to be accessible. whats my best plan of action here to have full coverage, using both modems, having devices register properly & not as moca incorrectly, and make stream work, and have landline still work lol sorry for the huge read but ive tried getting all these things fixed individually and usually the only real info i get is the affordability of xfinity mobile and how i should for sure get a phone and line through them. lol any help greatly appreciated