I hear that - metal tracks are great, but I only get them for tanks I really like. Got a lot of armor in my stash and metal tracking them all would be waaaay too expensive. Incidentally, I'm the opposite - I love assembling models, but painting them fills me with anxiety. I am however right there with you, that an outsider would think I hated modeling by listening to me at the workbench.
For vinyl, it depends on the track. I've had Tamiya vinyl that took paint no problem and never flaked or chipped, and I've had low-grade tracks that never accepted a single drop of glue or paint no matter what I did.
The only solution I've found for tracks that won't take paint is to make up a mixture of plaster, brown paint, pigment (optional) and artist's medium (optional), and mud the heck out of them. Then you can add lighter or darker layers on top of that. It kills the detail, but with low quality tracks, this may be a blessing.
Again, depending on the track material, switching up the paint you typically use may help. I've had a couple that wouldn't take acrylic, but took enamel and/or lacquer just fine.
I typically use pins in the hull for track sag. Never tried sewing and I glued my fingers together one too many times to enjoy gluing them down.
I've also taken a bit of a "good enough" stance lately. My free time is very much at a premium for various reasons, and the only person who will ever see my models and know anything is off about them is me, so I usually let things like track sag go unless it's really noticeable, like on a Panther or King Tiger.
Check out Tabletop Minions on YouTube, he may be helpful!
https://m.youtube.com/user/tabletopminions