Yes MoCA sounds like a good solution for you. It’s really simple. You do need two MoCA devices (think of one as a place for the Internet to get in and one for the Internet to get out to your computer). You can check online and see if your Modem has MoCA otherwise you need to buy two adapters.

If you find that your modem is MoCA, buy one adapter, connect it with coax to the coax near your computer, with Ethernet to your computer, and to power. The instructions will tell you how to pair it with your modem. It’s usually press a button on both sides or go into the UI and type a password.

If your modem is not MoCA, you need two MoCA adapters and it sounds like a coax splitter. Connect the wall coax to the splitter then connect your modem and the MoCA adapter with coax to the splitter. Connect the MoCA ethernet to the modem/router and connect power. Then follow the steps above for connecting the other side and pairing.

I’m not aware of an enclosure that has a problem running with open slots. I have a Synology unit that’s running with 3/8 empty bays.

I can speak to the Synology RS1221+ as I own two. They are great NASs but they are terrible at compute/transcode.

You missed an important detail which is how much data do you need to store?

Those big servers are nice and powerful if you can stomach the power bill.

My current setup is the two Synology’s in an HA pair for storage with a pair of similar spec Hyve servers for compute. If you’re looking for an all in one unit, the big server is the way to go.

You could have a combination of 2.5Gb going to your entire network.

Think of it this way. Your router aggregates all the traffic from your network to put over your WAN. Your WAN is your way to the Internet so you can only go as fast as your WAN.

It depends on what you mean by hub. I assume you mean some kind of ISP provided device? If so you’re probably fine up to the number of ports it has. If you’re out of ports you can buy a network switch, connect that to the ‘hub’, then connect more to the switch. Your biggest limitation will be internet speed but, depending on where you send that security camera footage, that may not be an issue at all.

TL;DR: Run the cable to the new place and install your camera. You’ll be fine.

Yes that’s normal. Until the computer knows what decryption key to use with that specific disk, the disk is basically gibberish. In a sense that’s good because anything you put on there is largely very private but bad because it’s a bit of an inconvenience and losing the decryption key means losing the data on the disk. Up to you.