I've noticed this company also has coax modems. I wonder if they will work better than MOCA adapters. I've tried MOCA at my house and the quality of the signal is not good, connection keeps dropping every 10-15 minutes for no apparent reason...

You may have had filters on your lines or just really poor quality connections/cables. I’ve been using MoCA in my home to bring internet up from my basement to the second floor for a few years and it’s been flawless. Consistent 1gbps, no drops, 1-2ms extra latency compared to Ethernet wired devices.