I am Chinese and I can confirm all my tracks with Traditional Chinese characters in file names and tags was supported perfectly by your firmware. I also have a few Japanese tracks which also have their names and tags info shown correctly.
I am not so sure with Simplified Chinese characters though. I would say even the stock iBasso firmwares sometimes cannot correctly display a few characters. I certainly won't lose sleep because of it.
Yeap for me both the simplified & traditional Chinese are able to read by the original iBasso 2.1 FW, I am not sure about the the other 2.1FW