Choose the effect for the actual task
Cropping removes pixels outside a selection. Rotation changes orientation. Blur softens detail, while pixelation creates blocks of color. Those effects are not interchangeable: use cropping for composition, and use a deliberate solid cover when information needs to be obscured.
Selections are manual
The area editors use a rectangle that you draw or specify with percentage fields. They do not find faces, text, or other objects automatically. Review the whole picture for details left outside the selection, and inspect the downloaded copy before sharing it.
Save useful intermediate copies
Edits are encoded in the selected output format. Saving a JPEG repeatedly can introduce additional artifacts; PNG can be a useful intermediate format when keeping pixels matters more than file size. Keep the unedited source so that a later crop or effect does not become irreversible for your only copy.