In terms of priority the plecs should go first because they are responsible for most of the bio load. The impact of the tetra in a 180G is so small I would just move them all but that's entirely up to you.
You are doing the right thing in waiting for the temp to settle but FWIW 1 or 2 degrees isn't a big deal.
You are doing the right thing in waiting for the temp to settle but FWIW 1 or 2 degrees isn't a big deal.