I recently got a cham a about a month ago and had the same questions. Apparently the baby meal worms bodies are too hard and can be hard for babies to chew and swallow. They also contain a lot of chitin... whatever that is? As for a baby, I think 1 to 2 week old crickets are fine. Maybe even some fruit flies or house flies to vary it up.
You can also get: Pheonix worms (they are pretty small) and small wax worms. I would hold off on any silk worms for now because they grow sooooo fast (learning that now).
My 2 veiled chams are about 8 weeks old now. I introduced a mealworm to see if it was time, and it seemed as if my male had a hard time eating the mealworm. I took the rest of them out as i do not think it's time. Right now i am feeding them strictly gutloaded 1/8th inch crickets.
I have never fed my cham a mealworm.
Too many problems involved.
Zophoba worms, however, are fantastic feeders.
At this age I was feeding mostly crickets and some waxworms. I know everyone warns about waxworms and their high fat content, but when you're feeding a baby 5 or 6 a week, I don't think it's such a big deal.
Phoenix worms are hard to digest unless you pierce them with a pin before feeding (they are high in Calcium). I think fruitflies are a waste of time at this stage.
One of the main reasons for offering a variety of feeders is that chameleons get bored. However, this doesn't really happen until they're quite a bit older.
So, I wouldn't really worry so much about variety early on, just concentrate on a good gut-load for the crickets.