Hi Alex,
Soft-Bodies have no “Tear” to my knowledge.
Cloth shows a tear, but it is not really torn apart. It just stops limiting edges to their length, simply said.
To have a Cloth reacting to a non Cloth object as Collider is a the way to go. It is action->reaction.
Two cloth reacting to each other at the same time is like an infinity loop, and so far I can tell, not the way this works.
Cloth reacts to each other layer by layer, and I would cache the lower (under shirt) then let the shirt react to it.
To gain more interactivity or precision, there are Sub-Sampling steps in the Expert tab, but that helps only to a certain degree.
If it would be one object, it might work with self-collision. Perhaps not really what works for your project.
I tried to set up something that delivers a collider as well, but as mentioned, each move on the first cloth would create an reaction on the other cloth, this reaction would affect the first cloth and so on, infinite sound perhaps hyperbolic, but I think it leads to a better understanding that way.
Again, this is not seen as a solution, more like an explanation, but perhaps it leads to something usable for your project:
https://www.amazon.com/clouddrive/share/sKcjrYqruVuNOSFTxO0akG2K5dFKkPkxDNWThOpHgtN?ref_=cd_ph_share_link_copy
Perhaps the answer is in a third cloth, between the two, reacting to all forces by itself (and alone), then get cached and act so as a collider to shape the reaction of the two main cloth. Note that the Cloth Cache Tool allows for manipulating the result.
https://help.maxon.net/#CACHETOOL
All the best
