An account is one worker. No phone, no emulator, no screen.
Each account gets its own session, websocket and worker thread. Refresh tokens rotate, so exactly one client may drive an account at a time.
Accounts can be created in bulk with your own SMSPool number, a Salamoonder solve and a card or Revolut key. Chrome is required for the bot-protected steps.
The API plan is the only one with account creation. It is also the fastest to scale and the easiest to run on a spare PC.