Those 2.5" drives use 5V, only 3.5" ones use 12V. The reason why the USB 2.0 one has 2 USB plugs is because a single USB 2.0 port doesn't provide the necessary current (amperage) to power the drive.
All the other ones are USB 3.0, and those ports do provide enough current. That's why you only need a single plug for those.
Also USB 3.0 enclosures/adapters will allow you to transfer data much faster than USB 2.0 ones. So I'd remove the first one from your shortlist right away.
If you are going to use that external drive on a regular basis, I'd suggest an enclosure. Adapters are good for when you're always messing around with different HDDs and need something to quickly plug them in to, but do little to protect the drive from dust etc.
Which one you choose is entirely up to you.