I'm looking at opening a small futures account, probably with NT or Amp. Also considering getting the IQFeed.

Do the brokers/FCM's typically require one to sign up for RT data for the markets one will trade even if I already have another RT feed?

Yes of course, not your charting is important, important is the connection between you, your broker (their clearing firm) and the exchange you want to place orders

You don't need a separate feed. You can just use the broker feed for your charts. An independent feed from a data company is good if you want extensive historical data for back testing but otherwise the historical data from a broker is enough for most people.
An exception would be the odd broker that bundles their data (such as Interactive Brokers I believe), so that it isn't any good for analysing accurately volume trading on the Bid or Offer, if you want to use footprint charts or Depths of Markets, DOMs, that split the prints; then a separate accurate data feed would be required.
As you say though that you are considering IQFeed, not that you already have it, you could save yourself a couple of hundred Dollars a month by considering whether you actually need it or if the broker feed will be perfectly fine for your needs.

Thanks, I will look at keeping fixed costs low. But in order to understand the typical setups I'm wondering if these FCM/brokers would allow me to trade a market without a real-time broker feed. Lets say I have two futures accounts with different brokers, would I be required to pay to sign up for RT feeds through both?

I know IB allows one to trade markets without having the RT feed through them, but as an example NT seems to indicate they do require one to pay for a NT RT feed if I read this correctly: (cannot post links, but I'm looking at the Ninja EurexContinuum info page)

Or lets say I have IQFeed and two futures accounts with NT/Amp style brokers, would I be required to pay for three RT feeds in order to place orders?