Where I’d like to standardize the size of every thumbnail across the board. But I don’t want to sacrifice quality or have it look really bad. Any suggestions?
If the images do not all have the same initial dimension ratio (say 2×1) then squeezing them into 1×1 will distort the thumbnails.
You can choose whether the thumbnails all have the same height OR width but not both at the same time if the dimension ratios are different (as it appears).