('sall good if you leave them as they are or not.)

Mitigation Power: It's the part you should already be knowing if you have the RT Fuse with or without this mod. In short; when your total stored power exceeds your Fuses' total mitigation power, the fuses get useless. No effect at all, doesn't protect from explosions (default RT Fuse job) or Battery Drain (this mod's job). So, you should always try to keep your total mitigation power above your batteries' total stored power.

Mitigation Power Multiplier: Remember how the RT Fuses have the standard 1800W mitigation power; this one multiplies it by the amount of you set. So when you increase it to the top, you can almost protect your whole power net with a single little circuit breaker.
Unfortunately, this setting doesn't change the fuse description, so even if you make it to 10*, your fuses will still show 1800W, [but they will have 18000W mitigation power] so the overall calculation is almost on you. For a more proper approach, Bigger Fuse mods are out there. (This bonus setting will be applied to them also.) This settings is more like a lazy approach if you didn't get the time to install other mods, want a quick change, or trying to be sure what you exactly want etc.
If you didn't especially feel the need for it, there is no reason for you to change this setting.

Surplus Mitigation Share: Removed with the new update.

Battery Drain without Fuse:
If the drain from one of your batteries under proper fuse mitigation is 100W;
If you set this to "Same"; Non-fused drain will be the same; 100W
If you set this to 3*Mitigated, when you don't have enough mitigation power, your drain will be 100W*3 = 300W. (If your battery has 250W stored, it'll lost all of it.)
If you leave it at default "total stored"; non-fused short circuits will drain all of your batteries.