X-Plane 12.00 Beta3
X-Plane 12.00 Release Notes Beta_3
X-Plane 12.00 Beta 3 is out, fixing over 20 bugs. Upgrade now.

Next, I conducted a test flight. Departing from Mammoth Yosemite Airport (KMMH),
I flew a Cirrus SR22 over Yosemite for about an hour. The simulation ran stably without any issues.

Landed safely back at Mammoth Yosemite Airport.
By the way, the ATC feature in X-Plane 12 is much more convenient than before.
You can communicate with Air Traffic Control at any time and request VFR landings. There are many more presets, so it is highly recommended.

Finally, here are a few recent screenshots from my aerial tours.
Beijing Capital International Airport
San Francisco
Las Vegas
Heathrow Airport
London

Regarding machine performance, opening Activity Monitor on macOS:
You can see all 16 GPU cores are running at maximum performance;
Only 4 out of 10 CPU cores were used, and the usage was below 50%;
Also, there is plenty of free memory.
It seems that X-Plane 12 requires a powerful GPU to achieve perfect visual quality.