File name length is limited by Commodore DOS, 14 characters iirc. Keep filenames uder that size and you should be fine.
The uiec is made to be as system friendly as possible and that is what makes it the best product! The load speed is close to that of a 1541 by design. You can speed this up tremendously with fast loaders such as JiffyDOS. I recommend you get jiffyDOS. If the program is not JiffyDOS friendly, you can disable and use at ~1541 speeds. If it is JiffyDOS friendly it will fly.