A SATA III SSD such as the Sandisk Extreme is no faster over USB-C 3.1 than USB 3. The SATA III SSD is the bottleneck.

Unless you need the portability, and SSD in a $20 portable dock gives you greater bang for the buck. One of these, for example (exact same SSD as the Sandisk Ultra, BTW)
https://www.amazon.com/dp/B073SBQMCX?aax...SBRHH6&th=1

in one of these
https://www.amazon.com/dp/B0185G6Q58/ref...2xpY2s9dHJ1ZQ==

Audiophile owners require a 2TB external to fit everything. If you install only Real Tracks and Drums onto your external like I, you need 1.1TB space so, again, the external needs to be 2TB.

If you have the Need for Speed and have a 2017 or later TB3 Mac, then the Samsung X5 is the ticket. There's no dock/enclosure that gives you the same bang for the buck. Available 500GB ($199), 1TB ($399) and 2TB ($799)

https://www.amazon.com/Samsung-Portable-SSD-Thunderbolt-MU-PB1T0B/dp/B07GBWZJFG/ref=sr_1_3?keywords=samsung+x5&qid=1568327112&s=electronics&sr=1-3
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BIAB 2020 Audiophile 2017 iMac Pro 2T SSDx2 Mojave; 2012 MBP Catalina
Overture 5 DP 10 LogicProX Finale 26, Encore 5.0.7 SmartScoreX2P Notion 6
Legacy G4-1K DP OS 10.4.11 / OS 9.2 Apps