does flashing a kernel ever wipe anything on the phone? + Doing it without CWM? does flashing a kernel ever wipe anything on the phone?

and is it ever dependent on android version?
e.g. 4.22 or 4.3

I have CWM and i've seen the option to install from zip within CWM recovery.

but is there a command with adb or fastboot to do flash the kernel? what is it?

Or do you pretty much have to install it via CWM>
No, flashing a kernel only wipes the old kernel. Generally, user-space drivers in the system image will be specific to a particular version of the kernel driver, and each kernel driver version will only work with certain kernel versions, so only flash a different kernel if you know that it was built to work with your user-space version, or vice-versa. Usually stock ROMs will only work with the kernel that came with the ROM, and third-party ROMs will say which kernels they work with.

On devices that support fastboot, you can use fastboot flash boot boot.img to flash the file boot.img to the boot partition. This is the one that stores the kernel.