The only officially supported device you can purchase for phone service is the TG862G. As a basic home router, it is fine, but has limitations if you want to do anything advanced. The wi-fi is limited to 2.4Ghz N mode, and you can't bridge the thing, unless Comcast does it for you (good luck)! Comcast will also use that gateway to broadcast their Xfinity Wi-Fi hotspot, but you can contact them to have it turned off.
I don't know anything about the TP-Link WAP, but if you want to use it along with the TG862G, just make sure you have it configured to use the 5.0Ghz band, and you should be fine.
Or, you could do like I have, and get a TM822 (just a cable modem EMTA, so will work with the phone service) and a separate router/AP. This is totally not supported, so you are on your own if anything goes wrong, and since it isn't an officially supported retail device, there is no warranty with the modem.
Wish there were more options, but with using the Comcast phone service, you're stuck with the equipment they use, which is a short list.