Some comments from my side without trying to sound agressive or anything, just in an educational note : )
Ok, first off, there is not such thing as "texture" for tone, there is texture for music composition and appreciation, but not for tone, as texture is a combination of characteristics in an arranged piece of music.
Second, what you describe as a richer sound, is called tone coloration, the "hi fi" sensation you feel from the amp its caused by the treble, that might be too high for the intended porpouse of the gear, an FRFR
Dynamics come from the kemper if you are using the FRFR section of the powercab, and very few dynamics come from the amp simulation, which I did not find impressive, the "amp in the room" sound is just a bass heavy EQ with a sharp cut on the 120 Hz area that makes the sound more omnidirectional without too much boomyness (You can get the same trough some EQing with any FRFR cab).
I did test the powercab when hunting for a FRFR, it was an instantaneous no-no for me.
As a recommendation, you should always try gear at rehearsal volume, as the powercab sounds tiny with a band (heard it before) and starts sounding digital with the amp cab simulations at higher volumes.
On the other side, glad you found something you liked : )
No one here has the same ears, and I can find something displeasing, you might find it just about right for your tastes. The powercab is a fine cab for modelers and kemper, but for me it was too expensive and also bulky for my needs. Try to tame the highs from the EQ out from your kemper a bit down to get the sound as flat as possible, compare with your reference monitors, you will enjoy having more uniformity on the eq across all your profiles, as most of them are pre-eqed to a perfectly usable sound.
I'm not a sound expert, all I can give is an advice based on 1: My ears 2: My tastes 3: My use (mostly home, as I'll only try it with my band next month, Tonejunkie/TAF presets mostly + RZ for high gain..) with - 4: My weak english level that makes me use terms that may not me very acurate.
I've seen many likes for the HR108 for home use, I've read them before buying it, and I could'nt get close of the tone I have with an amp + cab in the same room.
I felt the HR108 to be too smooth in the bad way, soften, I expect a gainy sound to be granular and a part of sound complexity and beauty comes with this. Furthermore the sound was very bassy and what I described as "colored", maybe the term was not well chosen: as if I was using a TS9 with gain on 0.... As I play 80% with the neck pickup of a strat, I just could'nt get used to that.
I agree that the high's are more (maybe too much) pronounced on the line 6, but I can get a similar tone and playability in FRFR mode as I get with my head+cab, at home friendly volumes, I'm not surprise I could sound tiny loud, and It could be for the same reason as it sounds good quieter..
Also, there is a huge difference between
1: Kemper merged profile taken with a head+greenback with the powercab in FRFR mode
2: Kemper same merged profile with cab disabled, with powercab in greenback mode
I could have thought it would be quite equivalent ... but the powercab cab sims seam to filter more highs than the Kemper cab section does. Powercab sims feel unnatural to me. I also get to the conclusion that the FRFR mode of the line 6 PC could not be so FRFR even if I like it.
Finally, nothing new here, as 3 Kemper profiles of the same amp can sound and play very different, 3 FRFR will also sound a feel different, tone seeking can be complex. I'm glad I kept my real amp, at least I have something to compare ...
And that said, even If i'm quite satisfied, these 2 FRFR are so different that I will try other solutions if I can, maybe the asc10, or the kemper active cab when it comes out...