The USB 2/USB 3/USB 3.1/USB-C/Thunderbolt/Thunderbolt 2/Thunderbolt 3 deal

Preamble

I'm going to buy a new computer and a few USB 3.0 external drives soon. I also have some USB 2.0 external drives.

I cannot get a grip on the USB 2/USB 3/USB 3.1/USB-C/Thunderbolt/Thunderbolt 2/Thunderbolt 3 deal.

In general, I'm just trying to get a handle on the compatibility aspects. I already know that data can only transmit as fast as the slowest device or cable, so you can more or less skip that part (unless I'm wrong here or not entirely right or it's more nuanced)! Here are my questions, potential set-up, and current set-up. The set ups might be unnecessary but I added them in before I realized this.

Questions

1) On the MacBook Pro 15.4" mid 2017, what do they mean by "Thunderbolt 3 via USB Type-C"?

2) Which ports can I connect my USB 2.0 external hard drives (whose ports are, I think, Micro USB B and USB Mini-b (5-pin)) to: Thunderbolt 2, Thunderbolt 3, USB 3.0, USB 3.1, and/or USB Type-C ports? Is there an adaptor for any of the remaining connections?

3) Which ports can I connect a USB 3.0 male end into: Thunderbolt 2, Thunderbolt 3, USB 3.0, USB 3.1, and/or USB Type-C ports? Is there an adaptor for any of the remaining connections?

4) What male-end of the Thunderbolts and the USBs is most compatible with the ports USB 2.0,Thunderbolt 2, Thunderbolt 3, USB 3.0, USB 3.1, and USB Type-C?

5) Which is the fastest? Thunderbolt 3, USB 3.0, USB 3.1, or USB Type-C?

Thank you

Potential new set up

Potential new computers and ports

MacBook Pro 15.4" mid 2015 Z0RF-MJLQ22

2 x Thunderbolt 2

2 x USB 3.0

MacBook Pro 15.4" mid 2017 MPTU2LL/A

4 x Thunderbolt 3 via USB Type-C

Potential new external drive

(USB 3.0) PNY Turbo Flash Drive 128GB P-FD128GTBOP-GE

1 x USB 3.0 (male)