Internet - security/networking

[FrogPD]

I am going to be getting internet at my new place. All the available options are cable, so no fiber. I’ll be getting Spectrum 400mbps. This is Los Angeles county, if that helps. 
 

This is what I am looking to do. I would like to add 3 security cameras. The unifi door bell, a front camera (probably g3) and a rear camera (at the garage). The rear might end up being the dome camera or two cameras facing both ways down the alley. The place is a town home. 
 

It’s not a super large home but the internet that is currently there doesn’t reach the whole home. So I am looking to add a unifi router and either a mesh or access points. 
 

With all that said, I am not network savvy. So I will be hiring a contractor to do the work as I’d need Ethernet ran to the camera locations and probably two additional ran to the bedroom so that I can have a wired connection to Apple TV and gaming console. 
 

Do I use the standard modem that spectrum supplies. It’s a router/modem combo or do I purchase my own modem. Not being network savvy I don’t know all the items I need. Just the items that look good. I like unifi cause I don’t wanna pay monthly for it. Does anyone here know any good networking people to contact that does home installation or what the best parts would be. I’m at a loss here. I just know the current setup needs to be rebooted daily which is a pain. Is as slow as dirt 18mbps. 
 

Thank you for your time. 

[skimmilk5]

Spectrum will provide you with a cable modem. Modem stands for MOdulator/DEModulator. Your modem is responsible for converting the signal that comes from your coaxial cable into an Ethernet. Your ISP may also provide you with a basic router. You don't want to use this. Instead, take the "Internet" cable from the router and plug it right into your Unifi Security Gateway's WAN port. Then, plug the rest of your network (switches, APs) into the LAN 1 port. It'd look something like this.

[FrogPD]

Since the modem provided by Spectrum is a combination router/modem. Is there a way to shut off the router functionality of it, or does simply plugging in a Unifi Security Gateway WAN port do that automatically? Is this Unifi security gateway better/worse than getting something like the Dream/Alien/AmplifiHD.

 

This gets confusing because there is Unifi, Amplify, and other names they go by.