For retail forex brokers, due to the small trade sizes, the broker will have to take the opposite of your trade and be your counterparty.
A broker can have access to an ECN, but that doesn’t mean that you, the client, have access to the ECN. More likely, this “ECN broker” is still taking the opposite side of your trade, and then hedging its risk in the ECN (or with another liquidity provider).
What’s important is if the prices you’re quoted are competitive and if you can get filled at that price (or better).
Just because the broker takes the opposite of your trade doesn’t necessarily mean that they’re evil. For retail FX traders, outside of futures, this is usually the only way to speculate in the FX market (because retail traders lack the credit relationships).
Yes, potential conflicts of interest arise but that’s why the regulatory jurisdiction where the broker operates is important, as well as execution quality and transparency by the broker itself.
Look for brokers who are regulated in the US, UK, EU, AU, and SG. You’ll filter a lot of shady brokers due to their stricter requirements.
From these brokers, see if they share execution quality reports.
And test drive their customer service to see how responsive they are.