I grew worms in containers for a short while and learned a lot about them. First and foremost, I learned it's nearly impossible to separate worms from their casings LOL. But, that's a long story.
If you added them to a raised bed that was on top of the ground - so when they ran out of stuff to eat in your bed, they could wander somewhere else - that would be great.
Worms are incredibly voracious. They can eat an enormous amount of food. Which, of course, they turn into compost for you. But, once they run out of food, they will go somewhere else.
If I had raised beds and was going to add worms to it, I'd mulch it heavily with leaves or shredded newspapers. You could even turn the newspaper into the soil. They'll eat it and turn it into castings for you.
They need to consume something, like birds do, to clear their gullet - I'm probably using the wrong term right now, as I'm tired and it's been a while. But, what you can do, is just add some powdered calcium to the soil for them, or you can dry and grind up egg shells, which is what I did. At the time, I was eating a lot of eggs, and I'd just put the shells into a paper bag and let them dry out, then put them into the blender and turn them into powder. If you add this to your beds, too, they'll also have something else they need.
They're fascinating creatures. But, I can tell you firsthand, that raising them for their castings is a lot harder to do than you might think. You will end up with their cocoons and baby worms in with your castings. And, I can also tell you from experience, you don't want a bunch of worms hatching in your indoor plant containers LOL. They will escape and end up in weird places.
As far as tea - I think that would be mostly a convenience thing. If your pots are full of soil and you don't have room for adding castings, then tea would be the way to go. Also, if you're not sure if there are any cocoons or baby worms in it, and it's going into a container where you don't want baby worms escaping, then tea is the way to go.
Honestly, I'm not so sold on the benefits of worm castings overall compared to other sources of fertilizer. I don't think they're cost-effective and/or worth the extra money. I do think adding worms to your compost pile is a surefire way to get it to compost much more quickly, though, and you can sell the worms to fishermen, depending on the type of worm.
