Same engine in all 2box systems...and you can use the same sounds on all modules.
There was a lot of work on the sounds added for the MKII...I am not 100 sure these sounds have been added on the DI3...on the current image. (But you can always download the MKII image...and pick the sounds if you have a DI3.
The Drumits are not using round robins...you can have sounds with 128 layers...and the engine will select from these samples. If you hit the drum exactly with 2 equal hits in a row...on layer 89...the engine will pick the layer 88 for the second hit...etc.
The samples are loaded directly from the SD card...when hitting a drum. So it is super fast to change big kits etc.
Best regards
Anders /
www.zourman.com