I have no comparisons as I think all distros ship the complete monolithic kernel. Of course specific IOT devices or Android ship a very much smaller kernel.
Building the kernel is not that hard, as you have kernel-devel which has all the sources.
You can use make menuconfig and see what all is enabled (as far as I understood this) and change stuff before compiling.
Monolithic kernels are pretty bad, see this excerpt of the interview with Jeremy Soller on RedoxOS.
So I dont mind memory or even less storage space, as the kernel poorly is not relevant at all here. I just care about keeping the root binary with access to all my stuff as small as possible.
I would love a system that detects the used hardware and then builds the correct small kernel for it. There are experiments making the CentOS LTS kernel work on Fedora, which would prevent many recompilations.