Since there are no restrictions put on your snap with classic confinement, you will not have any access problems. However, use of classic confinement is restricted and usually not needed. Access to dot files like we’ve been discussing is not a reason for classic confinement since either the snap can be adapted to work within the system or personal-files can be used (which is also restricted). This topic is discussing the suitability of certain uses of personal-files.
For your previous questions, SNAP_USER_DATA is versioned by snapd copies forward the data. If that doesn’t meet your use case, SNAP_USER_COMMON is not versioned and you can always choose to use that to store your artifacts. As for kubectl, you would need to ship that as part of your snap (which you would want to do anyway since there is no guarantee this will be available on the host even if you were using classic).