Fast And Cheap USB 3.1 Type-C SSD Drives For MacBook iMac
Many USB-C interface drives ship with both Type-A and Type-C cables for use on Apple computers old and new. When connected to a standard Type-A USB 3.0 port they'll operate with a maximum 5Gbps of available bandwidth. Depending on the SSD drive it may still perform identically.
A single SATA SSD is a fine match for USB 3.0 speeds. A dual SATA SSD RAID drive array is a somewhat better match for 10Gbps USB 3.1 Gen 2 bandwidth. It's only when you move into PCIe SSD modules or high-end multi-SSD drive arrays that you're best-off considering 20Gbps Thunderbolt 2 or 40Gbps Thunderbolt 3 storage solutions.
Honestly, unless you're a speed freak or have money to burn, the vast majority of Mac users just want affordable solutions that seem 'fast enough' for their computing needs - and fast and cheap USB 3.1 SSD external drives fit the bill perfectly.
It's Pro users - especially heavy video editing tasks that need and want high-performance, high-end storage solutions. Even then, they lean towards HDD hard drive arrays with huge multi-terabyle storage capacities to meet their needs. SSD-based arrays are only right when there's a massive budget available and storage needs are more modest - such as in music editing studios where file sizes aren't on the order of insane like 4K and 5K Ultra-HD video can be.