How will this router perform in a home theater setup?

So I am setting up my first home theater and I want to make sure that my router will be able to handle the load. I am in a small apartment but I will have a TV, Nvidia Shield, HD Home Run, Laptop, Desktop, and my phone. I am going to stream a lot and use PLEX/NETFLIX a lot.

Also I am looking for a solid DOCSIS 3 modem that works with Spectrum.

My router is the Asus AC-1900

 

Pretty much any SOHO router should be fine for local ethernet traffic - especially if it's Gigabit ethernet capable. Ethernet switching is a pretty trivial task and these days most things handle it at full capacity without a problem.

Wi-Fi can be more challenging, not particularly because of any given router, (though it is a factor,) but because Wi-Fi is an "only one thing at a time can transmit" technology and the more Wi-Fi devices you have, the more data you want to ship, the more competition there is for some "air time." (All Wi-Fi devices are receivers and transmitters and they all "compete" - it's anything but "fair" - for air time as they need it.) Thusly faster kit, both clients and AP/routers, and better signalling conditions improves the Wi-Fi usage experience.

Routing Internet traffic is a task that requires more computing power (in the router) so your need to check that the routers WAN-to-LAN capacity is in excess of your Internet service capacity. Some vendors cite the WAN-to-LAN routing capacity, but equally many don't You could also check out a US web site called SmallNetBuilder and see if he's tested your router - WAN-to-LAN routing capability is one of the metrics SNB tests.