Regarding tutorials, this series is pretty deep - well from my point of view, at least:
I’ve been using the MIDI Looper extensively for a couple of years, or rather intensely, because I only use a fraction of its potential.
For example, pattern saving, I only tried once. As far as I remember, it was rather straightforward to use, as described in the manual. I think - not sure it’s instant pattern change (i.e. it doesn’t wait for the end of the pattern to switch)
From the manual:
“The recorded loops for all 3 voices are a pattern. To change
between 12 different patterns, hold down the PLAY button
and press one of the voice buttons to select one of the three
patterns. There are four groups of three patterns and to access
a different pattern groups press one of the four smaller buttons
(LENGTH, QUANTIZE, VELOCITY, TRANSPOSE) while still
holding the PLAY button.”
And
“To save all patterns press FN+REC”
(I guess it answers some of your questions at least)
I like it because it’s simple and straightforward to use, not too many buttons, muscle memory comes quickly - which is important for live use.
I have considered switching to the RK008 - which is much more sophisticated - but I suspect it’s many buttons and features might distract me from the essential purpose (for me): looping parameter tweaks for basically anything.