Start with the distinction the category blurs. Where your call audio is processed and where your prospect records come from are two separate questions with two separate answers, and vendors reliably answer the first because it is the easier one.
An outbound tool hosted in Frankfurt that enriches contacts through a US data broker has not solved your problem. It has moved it one layer down, to a party you have no contract with and cannot audit.
The question to ask
Ask for the sub-processor list in writing, and ask specifically which parties touch prospect records. The length of the answer is the finding.
Two follow-ups separate a real answer from a badge. Which entity is the controller for the prospect data before it reaches you? If the vendor is, your outbound inherits their lawful basis while the liability for the send stays with you. And what happens to a record after an erasure request, in a system that sold that record to other customers too? Ask both in the same email. The distance between the two answers is usually where the exposure lives.
Derived versus stored
Dropcontact is the structurally interesting one on this list. It derives contact data rather than storing and reselling it, which is a materially different legal position from a database lookup. There is no retained profile to be the subject of an erasure request in the first place, which is a stronger answer than any residency commitment, because it removes the record rather than relocating it.
The trade is match rate on hard segments, so test it against your worst list rather than your best. A derived-data vendor evaluated on an easy list tells you nothing you will still believe in month three.
Screening is not compliance, but it is checkable
Cognism publishes that it screens against twelve DNC registries, named on its own compliance page. That is worth more than a page of badges, for one reason: it is falsifiable. You can ask which twelve. You can compare the list against the countries you actually call. And you can find out, before you sign, whether the coverage matches your territory or stops at the border of the vendor's home market.