Not sure if this is a macOS 10.13 issue or a 2017 MacBook USB-C issue or some combination thereof but file transfers to my Lexar S73 128 GB USB drive are extremely slow. This was a drive I formatted to exFAT on my 2017 iMac with 10.13. With the iMac I used it with USB-A, as it is a USB-A drive. With the MacBook, I have it running through a simple Elzo USB-A to USB-C adapter, which seems to work fine with everything else I throw at it. On the MacBook it seems to take a long time in preparation for the transfer, but then after the preparation finishes it transfers fairly quickly. However, with every single file, it has to prepare for quite a while. This appears to be dependent upon the size of the file. With 50 MB PowerPoint files it's very slow. With 0.2 MB Word files, it's just slow. On the 2017 iMac it was speedier IIRC. I know the USB drive is fine, since eventually I just reformatted it to FAT32 and it works fine that way (through that Elzo adapter). I can't use HFS+ or APFS though because this is for some PowerPoint presentations I'll need to be giving soon, and I want to be able to interface with Windows PCs if necessary. I plan on using the MacBook to give the talks, but at least one previous time, my MacBook with VGA dongle was incompatible with the VGA projector setup at one location (although it works fine with my VGA monitors).