Hello Xavier,
You are mentioning a very important point which is better not to add two bot together especially if they are trading the same Pair
Good to hear that you are making good progress and you are profitable.
When it comes to US residents. I’m no so sure but as long as you are accepted by a broker or a prop firm you should be good to go
The difference between the EA studio and the prop firm robots is that the prop firm robots will have more features like randomization which is good for props but the EA studio is good for back testing any EAs.
let me know if you still need help
cheers