I got a newer version of my previous router so I can still run the custom firmware. Thankfully setting it up went as smoothly as I could hope and with everything setup I still have plenty of settings storage for more settings. This means I'll be able to run more scripts and applications on my router to manage my network and keep everything working smoothly :)
I didn't bother going for a version with AX (wifi 6) because I don't have any devices that use it, the speed advantage is pretty small if anything and they are twice the price (over £300!)
You guys shouldn't notice any difference except I'll probably complain about router settings storage less, at least for a few years :D