The sounds being very similar to each other is due to the cab I'm afraid. If you want the best possible Kemper experience with the widest possible range of tones you need to use a speaker/cab that offers a flattish frequency response and enable the cab simulation on the Kemper side of things, a so called FRFR speaker. Otherwise you'll find most amps sound very similar, just as with other amps you'd find they all have a tendency to sound very samey through the same cab.
If you have studio monitors try using them instead with the cab enabled, or just use headphones, you should get something closer to the sounds you were after. If so then you know that you need to get yourself a monitor that's more suited to the task.
I have a pair of powered KRK Rokit-6 monitors and I will put them into place.Thanks for the suggestion. I'll switch to Monitor cab ON.