I have a mid 2015 rMBP, 2.6 GHz i7, 512 Gb flash drive & 16 Gb of RAM. I’m about to strip it down to just OSX, Pro Tools 2018 and Cubase Pro 9.5 for portable recording. Antelope is finally releasing a high-performance Thunderbolt driver for Windows so I’m moving back to my Win 7 PC with 4.4 GHz i7, 32 Gb of RAM, EVGA video card & 4K monitor. The rMBP will have High Sierra installed with a 120 Gb USB 3.0 external drive running Sierra for my Word, photos, email and social media.
It looks like a new MBP that supports 32 Gb of RAM is on the near horizon, but I ain’t going there.
I also have several USB 3.0 external hard drive boxes with 7200 rpm SATA drives for samples & recording along with an OWC USB 3.0 case for my Blu-ray burner. I’ve been running all these external drives connected through Anker USB 3.0 hubs finding no bottlenecks whatsoever. YMMV!