Currently, we are using simpler champions for this PBE test to focus on the basics of all champs feeling good over a specific champion feeling good (Ex: Using Spells, farming, laning, etc. over ensuring Yasuo knows his wombo combo or Evelynn being able to use her Ult to escape)
That said, we do want to ensure all popular champs and commonly seen champs are covered quickly after we launch to ensure players can learn to play against them prior to going into normals.
For the PBE Tech test though, I believe we will have a random mix of current bot champs along with new bot champs as we also wanted to have coverage of both while testing (and y'all are getting our testing champs for this launch :D).