This is my journey from the disappointment of how bad the purchased profiles sound to understanding the problem and the solution. Maybe it will also help someone ...
1. UNDERSTANDING WHAT WE HEAR.
If we hear a real amp in a sweet point, we do not hear the real sound of the equipment itself. We hear a mixture of speakers membrane sound with heavily modified freq characteristics of the speaker in the place where we stand + the amount of reflections from the room. If we listen to Kemper profiles on YouTube, they seem great to us because they sound similar to when we are standing in a room 3-4m from the amplifier. BUT ATTENTION: In the vast majority of sound examples on YouTube we hear sound directly from the KEMPER output to the DAW, which already sounds like Sweet point sound of amp + room. BUT IT'S A COMPLETELY DIFFERENT SOUND THAT COMING FROM THE SOURCE ITSELF. (The sound source in our case is the membrane of the speaker). You have to keep this in mind when you listen to YouTube demos.
(It's also better to just listen to the audio of the demo without watching the video. This way the sound can be evaluated much better. Try it...)
Such profiles sounds dull and covered when played live. This is because the sound of the source itself is replaced by the sound from the sweet point+room. But no worries. It will sound very suitable on the recording.
2. SOLUTION FOR LIVE PLAYING:
For this purpose, we need a profile made directly from the sound source. Therefore, if you want good sound for live performance, you need to use DIRECT or MERGED profiles. For these profiles, you must use IRs captured with a very close microphone to achieve the sound of the source. (one of the best IRs are for example on celestionplus.com). All you have to do is select the correct IR for the DIRECT profile. The RIG created in this way usually only needs to be fine-tuned to our taste.
3. EMERGENCY SOLUTION:
If you have purchased many STUDIO profiles or do not have the budget to buy new DIRECT profiles, the best way is to try to replace the CAB module with the most suitable
(or brighter) IR. If you don't have it first try to find more suitable CAB and then adjust Hi SHIFT, CHARACTER and PURE CAB. By combining these three parameters, very useful natural-sounding results can be achieved. Only then try adjust the EQ and DEFINITION in the AMP for the last fine-tuning of the sound. It is best not to use headphones, but rather monitors if possible. This procedure is not perfect, but usable results can be achieved (sometimes even very good results...)
FINAL THOUGHTS:
I had to understand that the profiles intended for use in a recording must be different from the live playing profiles. From a good profile for live playing, it is much easier to make a good profile for a studio work than vice versa. I must always keep this in mind when buying profiles.