It's interesting that Rand Paul and Tom Price keep bring up "insurance choice" and "high risk pools" to revive those plans that had low lifetime max and high deductibles. Very few providers would accept those plans before the ACA eliminated them altogether.
The $500 million in Medicaid services that goes to Planned Parenthood for women's well-care cannot be replaced by the existing system, so you are correct- the burden will shift to the emergency rooms and the already overburdened public health clinics.
One thing also to add that is a very important change from the ACA: it eliminated the segregation of medical and mental health services. All ACA plans had to cover mental health services under the medical benefit.
Why is this important? Because we have a jail system that is full of people who should be in drug and alcohol rehab programs. And we have a problem with opiate addictions in the very southern and midwestern states that elected Trump. By eliminating Medicaid coverage for these patients, we will shift the burden back to the very expensive criminal justice system.
There were some interesting articles in the press over the past year about how profitable some of the ACA plans were for the insurance companies. In the case of Aetna, they were caught lying to the press about why they pulled out from the Obamacare exchanges.... turns out they were trying to coerce the Justice Department into approving the merger with Humana.
Judge: Aetna lied about quitting Obamacare