TT is your only option here. It's the only platform that is fast and reliable enough to compete at the tick level. I've tried everything over the years but stuck with TT. CQG probably second when it comes to commodity spreads
for the cost difference between cqg / tt - cqg is plenty fast and tt has the worst customer service on the planet. however it took decades for them to get rid of someone working there finally, maybe they will come around.
Depends on how you define retail. For the average punter who gambles on the ES with a 10k account and slowly bleeds out or blows up once every two years solutions like TT are not viable. They should stick to the lowest cost solution because it doesn't make a difference, they lose anyways. But remember that there are profitable traders with a monthly P/L north of +10k who would not be profitable at all if they used trash solutions like Ninjatrader. If you do 10.000 lots in treasury spreads each month and you get sniped for half a tick on average because your platform is too slow, you'll be quick to pay 1.5k to TT or CQG because the costs outweight the slippage by a mile.
By definition, you trade under your own tax id, e.g. SSN or W-8Ben for foreigners, Queuing in an central exchange is a fair game, first come first serve, P&L doesn't really come into play, If you say TT is faster, I don't have facts to argue with that.
Since you already use Sierra Charts stay with them on AMP. It is not free however as you have to pay Sierra Charts $20 a month and you have to use Platform 10 I believe. I currently use this setup with CQG quotes and it works fine. The only problem is that if you use Delta Volume Bars, they only fill when the program is up and running. You can not go back historically like a minute based chart.