I bought two rolls of HD108 16bit LED Strip from NEWSTAR LED https://addressableledstrip.com/ 
one roll 60leds and one roll 144leds, in general, it's really an amazing product, The PWM LED vibration 27KHz is so beautiful and smooth; I really like this product. but I still have two confusions.

I control brightness of each channel with 5 bit current control also I control 16 bit for each channel; it is almost 21 bit control but not exactly. I guess the 5 bit current control is for white calibration of each R, G, and B channels, and the other 16 bits is for animations and such..?
Another thing is I thought I was able to control the LEDs with 40 MHz signal, the highest I was able to control was 18 MHz, Beyond 18 MHz I see some data corruption, I need to check again it is 18 MHz.

Did anyone test this HD108 16bit led also? No doubt it's a good chance to expand more markets by showing my experiments to my customers, I am just confused these two issues.