Buttons and ui elements in umg, i need help!

Ive been told its best practice to import assets in power of 2 ratio, do buttons have to be in that ratio as well?
im asking because its a bit annoying to import button graphics with a bunch of white space around them and makes it difficult to arrange and layout the elements.
should i just make every clickable graphic in dimensions of power of 2?

ex. a 512x 64 button, 128x64 tab etc. so there is no white space around the asset? Is this how it is done professionally? thanks!