Convert to JPG when the image is a photograph or doesn't need transparency. JPG provides better compression for photographic content and produces smaller files. If the image has text, sharp edges, or requires transparency, PNG would be a better choice.
For photographs, yes - significantly. JPG's compression is optimized for photos and can create much smaller files than GIF. For simple graphics with few colors, GIF might actually be smaller. Choose based on content type.
JPG doesn't support transparency. Transparent areas will be replaced with a solid color (usually white or black). If you need transparency, convert to PNG instead.
If the GIF was limited to 256 colors, JPG can't restore the original full-color data. However, JPG can display millions of colors, so future editing won't be restricted to GIF's color palette limitations.
No. Only convert static GIFs that are photographs or don't need transparency. Keep GIFs for animations, simple graphics, or images requiring transparency. Consider PNG for graphics and logos.