I have never heard of a switch alleviating wifi processing power. Too bad you don't have the source, I would have liked to read up more on that.
Best network setups depend on various factors. What your needs are, what hardware you have, and the setup of your house both for wired and wifi. I'll list a few things to consider and hopefully you find it useful. Make sure that netgear switch is not an an old 10/100 model that could cause bottle necking. Your router is a really good model and can handle great speeds and high loads for plenty of clients.
You would want your Wi-Fi router placed in a strategic location for coverage and avoid interference. Keep in mind that the signal is spread evenly around the router, imagine a big sphere, or circle. This is why a central placement will usually give best coverage of a house, but this all depends on where the signal is most needed and used, as well as the size of the location.
As far as interference, watch out for cordless house phones, microwaves especially, as well as speakers, radios, or other high power electrical devices that create strong electromagnetic fields. Microwaves emit the same 2,4ghz frequency as routers and often degrade signal the most when in use.
The switch would naturally go behind the router if it's only use is to provide more ports. There are some applications where the switch would be placed behind the modem instead. For example if you need more than 1 public IP or more than 1 internal network.
By having the switch behind the router, as long as your ISP provides you with more than one IP, you can have 1 port going to your TP-Link router, and a second port going to a second device. It could be a server on static IP, or a second router for example.
My home setup runs 2 separate routers, one is permanently connected to a VPN while the other is using the regular ISP routing. I do this by having a switch behind the modem, and to avoid double NAT issues (this is when you daisy chain two routers for example).
Cabling is a small detail Cat5 handles 100Mbps, Cat-5e 1Gbps, and Cat6 10Gpbs, so obviously you're unlikely to ever need more than Cat-5e even for 4k streaming of content.