Hey Bob,
Welcome to the community!
I’m not sure about the answer to your first question. Hopefully someone can cover this as I’m not sure and wouldn’t want to guess and lead you in the wrong direction.
Once you have let all the EA’s run on the demo account, you will pick the best ones to put on a live account. However, you should make sure that you ensure you still have a balanced portfolio on your live account. For example, let’s say you pick 3 EA’s.
EURUSD, GBPUSD, EURGBP
This will give you 2 of each currency pair.
If you have all of the same currency pair, I would just make sure that you only select EA’s that pass strict criteria (minimum number of trades, profit factor, etc.). You want to make sure that you don’t risk your real money with an EA that only has a couple trades.
I hope this helps you. Let me know how it goes. Best of luck in your trading!
Mark