Do I set up regular payments to my sellers in Bubble or in Stripe?

Is there a specific reason you want/need to use this method, rather than using using Direct or Destination charges, and doing the transfer to the seller accounts at the point of sale?

You can set up the connected account’s payout schedule to be once per month on any given date (using the monthly_anchor parameter), so they only get paid out on that date, which is much simpler that trying to do what you’re describing with separate charges and transfers.

But ff you really do need to use this method, then it’s perfectly possible, as long as the connected accounts are in the same geographical region as the platform account, using the Transfer API (I think the Bubble plugin even has this action.

But, in any case, you’ll need to get to grips with the Stripe Connect, and API docs (even if you’re using a plugin) so you know how to approach best it.