The 200 amps would be the entire service from the utility meter for a single family home. It’s definitely overkill on most houses but with the electrification of everything it’s probably for future proofing. Big houses or properties with multiple detached structures will occasionally have a 400 amp service but the utility meters they put on those are only rated for 320 amps continuous so I think 400 is also overkill for those types of properties usually.

Of course it’s plenty under the right conditions but it’s very easy to use insulated tools or gloves and not be at any risk of shock. Or you can work with the power shut off at the transformer or get the meter pulled. On the other hand you might not know you’ve created a situation that will burn down your house until way later and it’s too late. I’ve touched a 120v leg on a 200a bus by accident and barely felt a tingle in that situation. The expertise is not in trying to not be shocked because that’s the obvious risk. The less obvious risk is dying in a house fire because of an arcing connection somewhere that doesn’t cause a breaker or fuse to trip.

Not if this is the first disconnecting means after your meter. The green screw is bonding the bus bar to the panel and makes the neutral have a potential equal to that of the ground, so it is a ‘return’ path for the split phases to get 120V rather than the full 240V single phase that’s coming from the utility. If this isn’t the first panel after your meter you would isolate the neutrals from the ground/panel so you don’t create parallel paths for the electricity to flow during a lightning surge. https://imgur.com/a/zVSkSug

Let me also say that messing with your own house wiring the danger is not electrocuting yourself. There’s just not enough voltage to likely do that. The danger is making an improper connection that causes a fire and that’s why you should get a professional if you’re unsure and don’t understand the risks involved.

Looks kinda like a ballistics gel torso.

Too many people and too much advertising