So what conclusion may we draw from all of this?
You write a lot
Whether its from experience or not hard to say..without seeing any of your work...
My point in mentioning my last taiji teacher, was that it's part of my experience, he a reflection what I felt was
the closest representation of what is written in the classics that many "write" about but go crazy when skill sets are viewed.
small story :
Had brought a copy of the classics written in Chinese and English to the practice feeling I could use them as discussion
points from which to ask or clear up questions I had.
He looked at it smiled, and gave it back to me saying...
"its not really correct, will lead you in the wrong direction, that one should gain understanding through practice. "
Had thought maybe I was mistaken in understanding what he said, attempted to use it a couple of times, each time he gave it back to me laughing
it was funny
Others can make their own minds on this, just relating what was told to me, something I follow...
Understanding gained through practice
The history is interesting, in that it helps in understanding the beginning point of a practice, and maybe the view point of a teacher.
The OP had asked about training Chen style and Yang style concurrent training. In my teachers group we had Chen stylist with many yrs of practice among others stylist from different practices. They all had to drop what they knew in order to arrive at a different understanding...not asked to directly, those that did not that I knew in most cases couldn't get the skill sets they found interesting because it...
In my own case, understanding what I was looking for, dropped everything else to delve into this practice.
Was asked at one time if I had practiced Chen style due to my movement.
Never have, don't care much for it, looks and seems like some of the other CMA arts I've either practiced or know of. Realized from this comment I needed to examine my own movement, understand it and make changes as needed.
In my own path I had the good fortune to practice with / learn from direct students of public historical teachers allowing me to get a feel of the work from those closest to the source, helping me in understanding / clarifying what I was seeking..
It is also not because there was anything significantly different being taught or learned.
In fact Wang Yongquan as you quote below presents his material as Yang Style Tai Chi Chuan.
It is not a matter of dispute. And he states as point of fact what I mentioned earlier, there remain massive similarities to the parent arts in northern shaolin; "This is close to the practice and requirements of Changquan." -- to the point where many movements in Yang style come from changquan and not from chen style or a version of it.
This even this is nothing special; Wu Jianquan put some shuaijiao into wu style that isnt in chen or even yang style. Of course there are differences (as he points out the practical requirements are different) all I am pointing out is that what is being presented here, is really nothing special compared to any other school of tai chi.
Wouldn't agree from "experience" although it might seem so from the outside by those
writing from a comparative historical narrative
The Tung syle is quite different then the CMC style, the CMC is more in line with my practice now but also different...
Some of the people Li Jingwu trained with were known for skills in lin kong jing many considered magical. One such person was known to be able to point at a person and make them collapse (we're talking about trained martial artists here). It is aside these people, in the very same park, that these legendary figures and also that Zhang Yongliang and his teacher trained tai chi. With this knowledge, a lot of the mystery is removed and one can see that it's all really the same family and that if one works hard their dreams can be realized.
Carful about the "kong jin"
You mentioned the writings I use by Wang Yongquan, his method very close to what we practiced, is quite different
from other Yang family "stylist" that I've met studying directly under some of the present "yang family members" some of them
having many yrs of practice....
back to the OP.
.
Is it a good idea to study Yang style and Chen style at the same time
I would say depends on one's level and what they are looking for...
Don't feel they'er compatible practices although among some of the Chen lines outside of what seems to be the "family practice"
they may be quite similar, depending on what one is looking for it may not help in getting were ever "there" is for ones practice.