Noob question... A single mesh only has 2 ethernet ports right?
My living room currently has a tplink 4 port router that has my television, ip radio and Web cam wired connected to it.
If I use a mesh, I will just need to get a switch to link up my TV, ip radio and cam?
Ont-->mesh-->switch-->tv/ip radio / cam
You need to first establish which device is playing the router role. It could be the ONT or it could be the TPLink Router (i.e. although its called a router, it can also be configured in other modes such as access point/repeater/etc), depending on your ISP and setup. If unsure, login to the TPLink router and check what is the mode configured.
In general, any devices you want to add in the network would need to be after the router.