I think you mean MoCA, running data over unused coax lines. Assuming you have good coax cabling, a pair of MoCA adapters will be great. You want bonded MoCA 2.0 adapters. They run at up 1Gbps, and they actually do perform in real-world use. I measure 900Mbps+ among machines across MoCA at home in the rooms that I can't run ethernet. In my experience, Powerline wasn't anywhere near as fast, and it introduces its own problems with interference and stuff. Powerline shines when you have an outdoor structure that's connected via electricity, but not ethernet or coax. Both Powerline and MoCA support encryption, and each vendor has their own way to do it. (Usually via some web interface.)
These MoCA adapters work well:
Bonded MoCA 2.0 Network Adapter ECB6200 - Actiontec.com
for sale here:
https://www.amazon.com/Actiontec-Bonded-Ethernet-Adapter-ECB6200K02/dp/B013J7O3X0
They actually make a 2.5Gbps version, but they don't sell it to mere mortals, only service providers.
You will need one unit at your router, and one for every coax cable you want to convert to network data. See the picture on the page above. If you use splitters, they must be rated for high frequency (~2GHz) use, not TV signals. You should also avoid having any of the coax that you use for data connect with any other coax in the house, and especially the line back to the street. You don't want your network data literally spilling into the neighborhood, even if it's encrypted. If you can't avoid segregating the coax wiring, be sure to use a MoCA filter (basically just a one-way valve for the data stuff) at the point of entry. [Note that in the cable world, "POE" isn't Ethernet PoE, but "point of entry", and refers to the place where the cable enters your house.] Speaking of which, you will also need PoE injectors to get your cameras powered.
As you already know, avoid wifi altogether.
