How would one go about determining what effect to add for each cassette type? I don't know much about cassettes, I'm curious if this was something that could be done by ear or if these are commonly held opinions about the sound of each tape.

Again knowing nothing about tape, if I were tasked with this I would probably try to record the same audio to each of the tapes and then compare it with the original.

Similar to how the different film stocks affected the look of the image, the different tape formats would effect the sound similarly. Crudely explained, the more light brown the tape, the more noisy it would be. The darker the tape, the cleaner it could be. If you like the sound of someone standing behind you constantly saying shhhhhhhhhhhhhhhhhhhh, then choose a brown tape.

By now, the audiophiles have lots of profiles of what the various tape formats would sound like. It's been ages since I've looked at audio plugins, but I would be shocked if there's not presets to make your pristine audio sound like a Maxell cassette that's been played hundreds of times.

I was too young to do much with this information, but I not-so-vaguely recall my father cared deeply about getting metal-tapes. Not the music, but the material. I don't know if they lasted longer or sounded better (and now I would suspect: maybe have a sound profile he liked, rather than have high fidelity), but it was important to him.