Hey,
What are the major differences between the recommended 5.15 kernel and the latest non-experimental 5.19.13-1? Are there any performance advantages or better security? And what is the difference of 5.19.0_rt10-3 (Realtime) and the 5.19.13-1?
Did you try searching any of your questions? There is plenty of info what a realtime kernel is.
And there is https://kernelnewbies.org for various kernel changelogs (in a more readable format). Then there are news sites like phoronix.com where you can find articles about what’s new.
I don’t know what that is even. And 5.19 is neither of those. It’s EOL. You can google that too, or read on kernel.org.
Kernels are for hardware support. Newer kernels allow you to use newer hardware. But newer kernels sometimes introduce new bugs with older hardware. Install the newer kernel if you want, and test it. I would recommend leaving the older LTS kernel in place. If you have problems with the newer kernel you can boot into the old one and remove the newer one. Besides its a good practice to have two kernels installed in case of bugs or bad upgrades.