Good for you that movement you accomplished the 'plough' is one of my favorites since I was a teen, it stretches the lower back and relaxes the neck and shoulders and massages the organs.
I do not know Dahn yoga so I looked them up. There is a bit of negative information out about the founder and the program which seems to mostly deal with instructors and those in the organization. This means no_thing to me yet you may want to read some information and decide if it is an organization to be involved with even from the level of beginners course.
That having been said there is only one yoga, there are self styled yogas so that people might nake a name for themselves. Proper yoga dealing with physical mental and spiritual and pranayama will eliminate the root or cause of much emotional and physical pain perceived by the body.
As for flexibility it is all in the mind. The more open my mind becomes the more flexible my body is. Same for anyone.