Why is there an uppers trophy ( ' ) for some void champs..

That would be an "apostrophe", and in this case is often used to make a name sound more exotic or foreign, or simply to help separate the sounds.

Vel'Koz, Kog'Maw*

At least spell them right.

It's not an uppers trophy. It's apostrophe.

Well based on the Rek'Sai lore (HAH) the first part of the apostrophe is like their first name, their personal identifier, while the part afterwards is a last name, showing what species they come from (Rek'SAI is queen of the Xer'SAI)