A kemper through a guitar cabinet sounds great at low volumes. However, nothing beats the air pushing of a volume at the sweet spot.
playing with a good pair of headphones can be really nice for stereo separation and all the convenience, but also ear fatiguing, lack of string acoustic reinforcement, sounding too hi-fi, harsh, etc
As a reference, I manage to play the kemper into a Waza tube amp expander as power amp going into a Zilla 1x12 mini modern + a 2x12 MESA roadking cabinet at a good volume (cant hear my strings) , without bothering people. However I have a very chill girlfriend, cool neighbours and a tiny room that doesn't require much power to "fill it up".