What to avoid. It's more what to avoid such as chewing gum; bagels, raw carrots, hard candies and nuts; opening wide with big sandwiches; etc. Short term-nsaid's (if you can take them), hot moist heat; see a dentist who has extensive experience and training treating patients with tmd\tmjoint dysfunction for long term results.
TMJ and food. I guess they mean to eat soft food ( non chewy)so the patient does not need to chew too hard or too much. Patients are advised to avoid chewing gum or eating hard, chewy, or crunchy foods such as raw vegetables, candy, or nuts. Foods that require opening the mouth widely, such as a big hamburger, are also not recommended.
No pain. You can chew anything that does not cause pain either during or after chewing.
Depends on severity. If you consider chewy foods- gum, candy, taffy, etc., then non chewy foods will be the type don't tax your jaw joints too much during function. I would look up food consistency charts on the web and get some answers.
Many things. I would eat things that you can swallow with out really chewing such as cottage cheese, scrambled eggs, apple sauce, etc. Avoid crusty breads, steak, raw veggies, and the like. Make sure whatever you eat is healthy with high protein, and calcium. You may want to supplement with a multivitamin as well.