This mod, as the name suggests, aims to prevent mobs from being affected by daylight, that is, not burning under the sun.
It's needed only server-side.
Sure.
The actual difference is tick performance. Mob Sunscreen mod tries to clear fire on every tick (20 ticks = 1 second) on each mob while the game tries to burn them under the sun (check here). This behavior makes tick performance worse. But this is unnecessary because Minecraft already provides a clean way to do this. Protect Mobs From Daylight mod implements this way by turning off the mobs' burning under the sun. For more information, you can check the mentioned code here.
