connecting a second wired router ASUS RT-AC68R

@RB_MD​ Thank you for the link.   I have an amateur understanding of the extender/access point pros and cons.   I am ok with using it as an extender, it's only me and my wife in the house and we are relatively low-data users.   Seamless connectivity is attractive.   Frankly my most immediate need is just getting good signal to a garage door opener.   Beyond that it would be nice if our devices would stop dropping wifi and shifting to LTE data at that end of the house.   I've watched several how-to videos, I understand I need to make DHCP and IP assignment changes.   But there are a million settings on the gateway, and I'm just leery of tinkering without specific detailed instructions.    I was hoping this would be a common enough request that xfinity would have an article already written.    Thank you again.