Question for Amp Designers

I’m not an amp designer, but have built many tube and s/s for myself and friends.
There are too many parameters/factors to list that can do the above.
Just a couple for the
"laid back, mellow, & slower" can be.

limited bandwith
high impedance output (low damping factor)
little or no feedback, (creating the low damping factor)
Induced 2nd harmonic distortion
poor current ability
high impedance power supply (eg: tube reg)

and many more
Cheers George