So, this is my search setting:

Key points:
1. I use similar content search with threshold of 80.
2. I checked "between folders only" and I have two folders. So it should only compare the images from folder 1 and folder2.
Here is the result:

Three problems:
1. it still compares images from the same folder despite I checked "between folders only".
2. it shows a pair that with similarity of only 66, which is lower than my threshold.
3. The "sort by" at the bottom simply does not work. Choose any of them won't actually re-order the table/list.