My experience with AMP was it was a little struggle to get options set up on Rithmic - initially the person I was dealing with thought that only the CGQ feed suooorted options. They only support buying options. No writing or spreads.
GAIN via their own futuresonline sign up claim to support...
Base decisions on traded volume, i.e. the Footprint. What has HAPPENED. Not what people are advertising as their intentions (or not). Matt's link explains this well. The tape has happened. The DOM is what might happen.
This may help:
https://www.sierrachart.com/index.php?page=doc/InteractiveBrokers.php#TrueRealTimeData
If you care about analysing order flow data - the impact of volume traded at the bid or ask at each price level, then you will need accurate tick by tick data, not snapshots.
Having played with these for a week or two (monitoring order flow on ES but trading MES) there is a satisfaction in trading large multi-lot positions as described in the article's 'benefit 2 - scaling' but the commissions and CQG/Rithmic fees are horrible. A nice compromise is starting with 1-2...