I'm not sure about size, but here's my experience.
I started with a 15 gallon smart pot, then added another 20 or 25 gallon pot. Both are sitting on stands, which are sitting in appropriately sized saucers. The saucers were intended to capture leachate. The design of the smart pot allows the soil near the cloth to dry out; I have not yet gathered leachate from my bin.
I haven't harvested yet, so can't help there. Since starting the worms, I needed soil for some transplants. The earth worm compost is working great. That said, using the smart pots, the casual observer can easily see a 1-3 inch area of soil next to the edge of then pot that the worms don't process. I think it's just too dry. For my base mix, I used coco. The coco coir creates a 1-3 inch fluffy, brown layer near the edge; the processed ewc is a different consistency and dark black.
My most recent iteration of the design uses a 50 gallon smart pot, called the junior (22.00 on amazon). It's 36 inches diameter by 12 deep. It will probably be placed on pallets covered with panda film that would catch and funnel any leachate to a tote. I do not really expect much leachate from the larger pot, given my experience with the smaller ones. But, the larger one will have a way to catch liquid, should it be produced.
The coco coir went into the pot. Food for the worms is added either generally across the entire surface, (if using a ground worm meal type product), or in little holes that are covered with coco and the mulches..
A thick layer of rice hulls were placed over the worm bed; when I wanted to add or check something, I would scrape away the rice hull layer. Overtime, this is broken down by the worms, but in the interim it creates a great base layer. A thick layer of hay, which was innocculated in a compost tea (old ewc, fresh ewc, liquid and solid fish compost, humic acids, bokashi, crushed oyster shell, guano. Anything that can go into the grow can go into the compost tea and worm bin, I've found.
This site has a vermicomposting thread in the organic sections, I believe. Check it out. It's a wealth of knowledge.
peace