Sorry this has taken so long…. Have been tied up with new projects.
Regarding using TS connector on a transformer output, if the transformer is wired correctly with the secondary wired between tip and ring, then ATS connection is perfectly OK and just as good as a balanced TRS connection. The problem that you imply is if the transformer has a grounded centre-tap. In that case then the output would be shorted out with a TS connection. That situation is unlikely as nowadays the secondary winding would not have a ground connection.