Thankfully, this didn't come up for DC20 or DC17. I'm not sure either of them would have been ready for living away from home without a structured program like PEG.

My own experiences were pretty good overall--much better than being at grade level (alternated homeschool and traditional school at grade level depending on where we were living at the time). Rather than leave home before 18, I audited classes at the local university (no credit, so I could stay a freshman for scholarship purposes later), attended weekly department lectures, and did research (started around 10). It really helped me to keep going intellectually without having to move away/give up scholarships/pick a career that early. Around 15, I started shadowing, doing more substantial research, and interning away from home for a few weeks a year (on my own or staying with family).

It was a good set-up for full-time enrollment in my later teens, as I was able to pass out of most introductory classes/some upper division classes and take a wider variety of classes at a higher level without giving up scholarships and a chance to attend a rigorous college.

As for MD-only and MD/PhD programs, I'm in an MD/PhD program right now. My medical school class had some kids as young as 19 or 20 when we started medical school, some of whom had taken a year or two off after college to gain more clinical experiences (problems volunteering during college due to young age). It seems to have worked out well for them, and they will still be able to finish medical school relatively early.