Not sure there is a difference between arcade and prop shop!
I used to work at a prop shop, they trained a bunch of new grads or fairly inexperienced traders and then let them lose on the market. We did get a salary, not amazing but above national avg and then got a 50% cut of our p/l. I know at other prop shops they used to pay their traders nothing in terms of basic but they'd get an 80% cut of the profits.
The other aspect and this may be where the distinction comes in, there are also customer traders. These are people who pay for a desk and related set-up (screens, bloomie etc) but they keep all their profit.....well kinda. The fee per lot will include a margin that goes to the firm. Maybe a pure arcade is one where it is just customer traders? But I'd hazard a guess they are 2 terms describing the same thing.