By the way, it seems that Mimas does not support OTG. I just tried the same usb-c flash drive I used successfully with Note 2 (therefore this is not off-topic) - nothing happens. And I see no option to enable OTG.
Well, it has a working card slot, and I have several 256 GB cards, so who cares
It probably would work with 512 GB as well.
As to note taking - I am very reluctant to try. Both Mimas and Note 2 have screen protectors included, so you know...
Besides, I would not know how good it is anyway.