I also made LCD version of tinyBasic computer very long time ago in dog year. I remember the main reason why I have not used it well was "slowness" compared to OLED. This time I found improved graphic library PDQ in hackaday.com and I switched from Adafruit_GFX to PDQ.

PDQ_GFX version source is available here.

Actually really significant speed up is confirmed. You will see in the following movie..