Newbie trying to setup mesh

I am a relative newbie to openwrt and so far I have successfully setup a TP-LINK Archer C7 v5 with firmware OpenWrt 18.06.2 r7676-cddd7b4c77 / LuCI openwrt-18.06 branch (git-19.020.41695-6f6641d)
Now I am trying to setup a mesh network using a second AP TP-Link TL-WDR4300 v1 with the same firmware and I am not able to get it to work. I havent had a lot of time and I cant seem to find a straight forward tutorial. The 2 sites I looked at are below but either I am missing something as I follow them or maybe they don't work because one of my AP is AC and the other is N. I have no idea and hoping someone could please guide me in the right direction? I am also worried about affecting the house internet while I am messing around as the family cant live without the internet for more than 10 minutes.

With only two stations, there isn't any advantage to a "mesh" There's no alternate path between them. Only once you have three or more does "mesh" have an advantage.

For simple setups, WDS can work well

If that doesn't meet your needs, come back again. batman-adv configuration has changed significantly in the last few months (for the better) and many online references are outdated. is current at this time.

Thanks I will try the WDS though I did want to try the mesh. I understood mesh would have all the access points with the same SSID and clients could transfer between them easier.

Yes definitely run WDS here. You only need to enable WDS on the main router's AP then leave it alone while you work on the other one. Family members can always make regular connections (non WDS) to that AP.

As for the second router, set it up as a "dumb AP." The networking is the same except that the link between the two routers will be wireless instead of a LAN cable. Attach the WDS STA to the LAN bridge.

You can set the SSID of all the user access points the same whether the linking between routers is WDS, mesh, or wired.

If you had more than two routers (but not a large number) and want a true mesh throughout the house, it's simpler to use the internal routing built into mode mesh instead of BATMAN. BATMAN is kind of geared toward city-wide meshes.