What is the fastest/most efficient way to transfer 50GB data folder from SSD to thumb drive?
Bluetooth, WiFi and your screen have absolutely nothing to do with the transfer speed of USB.  Tweaking these settings in the hopes of making USB transfers more efficient is like waxing your car to get better fuel efficiency.


  The thumb drive is a garden variety of 64GB Lexar™


Is it a USB 2.0 or 3.0 thumb drive?  You can tell if it has a blue tab in the USB connector. That'll be the kicker.  If it's a 2.0, the maximum throughput you're going to get is 480Mbps.  Going downhill. With a tailwind. On greased skis.

If it's USB 3, you'll get at most 5x the rate of 2.0, but more like only 3x.  

As far as defragging your drive, that won't make any difference on an SSD with HFS+ format.  Plus PCIe drives run about 24Gb/s or 4x faster than SATA III at 6Gb/s