What is the difference between a Mini Segway and a Hoverboard?

None whatsoever. The two terms are interchangeable.
The word “Mini Swegway” borrows from the term Segway. When companies use the words Swegway instead of Segway, they simply hope for a recall effect on the potential buyer.
A few years ago, an American company selling hoverboards, simply inserted the letter “w” after the letter “S”. This is how the naming confusion started.
Perhaps you remember the company Segway which in the year 2001 introduced a new transporting device with a long handlebar.
The word Segway is derived from the word segue (smooth transition). This machine instinctively calculated the movements of the rider and took over his or her balancing.
Some of the same balancing principles apply to the hoverboard. It therefore made marketing sense to lean on the word Segway a bit.
Note: A hoverboard and a Swegway is one and the same.

Swegway or Hoverboard – Which one should I choose?

Again, there is no difference between the two items. Read above.
Hoverboards come under a lot of different guises. Segboard, Self Balancing Scooter, E-scooter, Segway Board, Mini Scooter, Back to the Future Hoverboard, the list goes on.

What wheel size should I buy?

Please check our model comparison. This should help you to make your mind up.
Even standard models come with different features, some have bluetooth in-built like our Mini Swegway “Luft” (pronounced Looft), or variable drive mode to set speeds, others have inflatable tyres.

How do I fit the charging cable into the Hoverboard port ?

The charging port has three pins onto which the charging head is fitted. To place it correctly try to find the the groove on the head and turn it until it fits into the largest gap between the three pins.