The non-NFA plugins (Oanda, MT4, etc) have an "enter trade exit trade" interface to the broker. So individual trades must be managed.
The NFA plugins (IB, etc) have an "order placement" interface to the broker. You place orders to change position. Position tracking is especially useful here. There is no need to manage individual "trades".
These have implications on how you should program your script for live trading.
Further reading:
https://zorro-project.com/manual/en/trading.htmhttps://zorro-project.com/manual/en/hedge.htmhttps://zorro-project.com/manual/en/buylong.htmhttps://zorro-project.com/manual/en/trademode.htm
