You got picsReturns, I went with 1" slip outside of the tank in order to use street 90's for a lower profile to the wall and 1" threaded inside the tank that immediately splits to two 1/2" loclines.
Overflow, both sides 1" slip so that I didn't have to worry about adjusting the bh if the threads didn't align in the direction the pipe was headed. Glued on the outside, press fit inside the overflow.