Can I set up the router as a bridge so that it works like I am connecting to my main router directly? Yes, GL.iNet routers work in router mode by default, which will create a separated subnet for you.

Your router is a radio transmitter, and where possible, you should try and have a clear ‘line of sight’ from the router to devices that require a fast connection, without thick walls in the way.

[Vadim] wrote up this short but sweet tutorial on getting started with the Vocore (tiny) OpenWRT-router-on-a-stamp. If you need more computing power than you can get with an ESP8266, and you want a… ...

Yes, having a wireless router is the easiest solution. Set up a wireless network with the help of a router, connecting it to your modem and then to all your wireless devices.