Edit: reply to OP, just agreeing with
@TacticalDillhole
My advice is if it doesn't move, wire it in. WiFi airtime is a shared medium, only one device can transmit at a time per channel.
Even though you have a 2-year old ASUS, it's still better than the hot garbage built into that Centurylink box. If you can site it somewhere in the middle of the house, you should get good coverage. Once it's set up, you should be able to disable the radio on the Centurylink box (it will only cause a problem at that point).
My primary AP is at the top of the basement stairwell in a center-hall colonial, at half power I've got >600Mb throughput everywhere except my back and side yard (-70 dBm for the nerds).
Free way to measure this is with a utility called Fing (available on Android/Apple appstore) or Wifi Analyzer (Windows). Fire it up and walk around. Awesome is -30dBm. Unusable is -90. -70 is the limit of where the radios try to get smart and downspeed your connection to preserve it. Adjust the power on your AP accordingly... adjusting it so you're getting -70 at the furthest spots you intend to use it is best.
On your concerns about power, far be it from one dad to tell another one how to parent. You do you. For comparison purposes, though, an FCC-certified WiFi AP at -30dBm (1W, max power, 6" away from the AP) has the same radiation density (SAR) as an iPhone 8/X/11 sitting about 8 feet away. 9 feet away from a full-power AP is roughly equivalent to a 4G LTE signal from a tower 2 miles away.
If it's got a radio, like the TVs, either disable or force it to join your wifi (preferably on a different SSID than you have real computers on). Without being associated, they'll continuously beacon out looking for an open SSID and dirty up the spectrum- like some idiot constantly keying the mike wondering if someone wants to talk. Oh, and those little devices... if they have a "made in China" sticker on them and no FCC certification, there's no guarantee they're not burping out RF all over the spectrum. I've seen small chinesium "wifi" devices take out (multiple) hospitals' wireless in the ER area- that's no joke.
If the Asus is smart enough to auto-select a channel, let it... even 200 yards away, your neighbor's wifi is gumming up your spectrum. If it's not, pick a different channel manually. 5Ghz can help here. If the Asus has something called "band steering", turn that on. If a device is capable of using 5GHz, it will be forced off of the noisy 2.4GHz spectrum.
