At the risk of stating the obvious, make sure to monitor in the context you want the Kemper to match the amp.
For example, if the goal of your profile is to replicate the mic'd sound in monitors then create the profile comparing "amp => guitar cab => mic => monitors => ears" to "kemper with cab emulation => monitors => ears" to evaluate how close you are (and when you can finally stop refining). If the goal is an amp in the room sound using a regular guitar cabinet you'll ideally want to compare "amp => guitar cab => ears" with "kemper without cab emulation => guitar cab => ears".
If your goal is both, then create one profile for each use case. YMMV.