

If you’re just running it in AP mode and extending from your base router you will be better off than if it’s your WAN device. I don’t know enough about these exploits to know how they are executed, so I can’t give you a solid answer, but I think it’s best to err on the side of caution when it comes to your data security.
If you’re fairly tech savvy and willing to put in a little effort, you can flash the firmware on the TP-Link with something open source like openWRT and that would eliminate any exploits directly caused by their coding. I haven’t done this in years, but I’m sure there are plenty of guides to walk you through this. It would require resetting up your network, but you’d need to do that if you replaced anyway.
Personally, I would replace the device with something higher quality. I don’t have recommendations for you, but I’m sure there are some resources you can find with security minded device recommendations. For “pro-sumer” grade stuff, where it’s better than your off the shelf options but not enterprise grade, I’ve heard Unify is a good option, but it’s complicated and expensive.
I host a Plex server and only use it to stream video. I don’t use any other features built into Plex. I’ve never had a an issue that I haven’t caused myself, and have a dozen people that share my library remotely.
I haven’t read about specifics in a long time, but I thought at one point jellyfin didn’t support remote streaming, which immediately makes in not an option. At this point it will take something more significant to get me to take the hours required to migrate everything out of Plex to a different solution, but are there any drop dead reasons why I should move now other than not being able to use the watch together feature that I’ve never used, although I disappointed they removed it, because it’s a nice feature?