Use png when your image has sharp corners (text, graphics, etc.). Use jpg for photos etc…
They are two different formats made for different purposes. (You will get the block-artifacts in jpg when using sharp corners and high compression, using png for camera-pictures will create large files).
Or use a modern format like webp or jpgxl, but some devices don’t support these formats so most things online are still jpg/png.
And if you have a vector image instead of raster use svg









Had a long flight this year (~10h) and got “real” silverware in a economy seat (but no real plates). The knife wasn’t really sharp but it did it’s job (edit: just checked my photos, it was a butter knife, can share the photo if requested)