Adam Mizner on internal concepts of Peng, Lu, Ji, An

Adam Mizner is a taiji chuan practitioner known for a focus on martial applications of internal principles.

https://www.youtube.com/watch?v=ieNSSp42MG0

https://www.youtube.com/watch?v=4nq0X9O7ryo

Start here,
There is much more

Lol. Well, that was a shred-fest. ;)
But based on that old RSF discussion, there seems to be a split in opinion whether it's all empty force and overly compliant ukes, or some good basic skills but overly compliant ukes. I'd think one would want to feel him first before making a judgement.

Empty force in CMA parlance means "no touch'' similar to Ueshiba and now Ushiro Kenji and others doing the wavy arm, uke fall down crap.
But I get what you mean.
As far as the real world goes.... when it comes to internals and aiki? (I'm not talking fighting skills, that's a different topic altogether) There are certain *tels* when you watch people move other people, which I don't like sharing much on line. They reveal where the teachers center is and where his ability to generate force is coming from and where he is neutralizing. Many, many times you can size someone up in a moment. Which makes it a whole lot of fun to take many budo people apart since the "feel" of them is even more revealing than the other failures you can assess visually on the spot. There are entire hosts of budo-ka who can't even stand balanced in their own bodies.... without any force on them. They are shot full of openings for kuzushi...and they're teachers!!!
For other things; levels of real connection, internal manipulation, creation and sustaining aiki past a waza, you might not really know until you do feel them.