You don’t need a worm bin, worms could be hatch from eggs in the EWC you get, if you get high quality castings but for the worms I have ......
Those worms came from a few handfuls of compost from my worm bin .... they will breed and grow in the earthbox .....
The minimum pound of worms could do four juniors easy - even eight, they will reproduce in the box - ideal environment for them - you could use box as a bin if you like and reuse soil - there is your bin ....
I can’t speak for differences between worm and non worm grows but outdoors it makes one heck of a difference - I pull a shovel of dirt and when I see 10 worms I have good soil - 20 worms I’ve got great soil, for sure it makes a difference .... AND in the earthbox since it is anaerobic the worms should help the aeration so in theory worms make a difference - more airways, food delivery specialists and they make fertilizer- what’s not to like .... but you’ll grow fine Flippin “onions” in the “box” no matter .... worms are an option not a requirement....
Handfuls of straw, enough to cover the soil - Kashi I do a few spoonfuls, one on each end - sprinkle all over the straw which is usually over compost - when the pole goes down and the worms have eaten the straw, time for more - I might add half cupful of compost between and a sprinkle of Kashi - sorry my brain kinda is scattered on the exact schedule - I just kinds read the worms and see how they are doing and add Kashi or craft blend or and kelp as I think at the time, sorry no real game, I’m kinda reading the worms and plant cycle - for example around day 30 I sprinkled some bat guano on top along with some bud specific compost - and just recently I added more guano and compost, Kashi and straw ....
Hope this helps,
MOB