With this naming:
test_tv/
├── MGM Cartoons (1934)
│ └── Season 1940
│ └── MGM Cartoons (1934) - S1940E02.mkv
└── Tom and Jerry (1940)
└── Season 1940
└── Tom and Jerry (1940) - S1940E01.mkv
And each series configured to use TheTVDB (Aired) episode ordering, I get the correct metadata for each:
I’m curious to see a specific example of a failure scenario for you (naming and folder organization) and how you have your library and series episode ordering configured.
Also, stick with either or your (1) or (3) scenarios above; symbolic links are problematic in my experience and a .plexmatch would seem to be completely unnecessary here, assuming correct naming.

