Confused about Charts required for Multi-Instrument Strategy

[AnotherTrader]

Say I wish to trade “live” a Multi-Instrument Strategy with two instruments, SPY (BarsInProgress = 0) and QQQQ (BarsInProgress = 1).


Which of the following is the correct way to do this once connected to the broker's data stream?

1. Open BOTH the chart for SPY AND also the chart for QQQQ, and set up the strategy on the SPY chart (i.e. even though the strategy runs on the SPY chart, the QQQQ chart must also be open); or
2. Open JUST the SPY chart, and set up the strategy on the SPY chart (i.e. there is no need to open also a QQQQ chart, as long as the QQQQ price data is available in the broker’s data stream).

I hope it is clear what's confusing me!
Thanks.

[NinjaTrader_Bertrand]

AnotherTrader, you would apply the strategy to the primary series, in your case the SPY - the strategy would the load the added internal series on its own via code, there's no need to chart all symbols referenced.

[AnotherTrader]

Many thanks.