The issue with Ucglib should be solved in 0.4.15 branch Rev 190.
I have not tested it very much so not sure if evrything is working properly.
But I think this library should be even slower as it uses 18 bit RGB pixel mode (3 bytes per pixel), while Adafruit uses 16 bit mode (2 bytes).
The fact that it was faster is sprobably because it was not working properly.
One thing that slows down simulation speed is that SCK output in Arduino Uno is where the board led is connected.
And simulating a led at 8 MHz takes a lot of cpu.
If you use an Atmega328 instead it will run much faster.
Simulating this dispaly will be slow in any case as it is using 8 MHz SPI clock, and no way the simulator can keep that at real time when it is continuously sending data.
A posible solution for this would be implementing some kind of "virtual" SPI conection, the same way that Serial Monitor or Serial Port connections are done.