2 stroke is the lightest in weight if that is an issue.
2 stroke produces more power for weight.
2 stroke produces no more Greenhouse gasses than 4stroke. Remember that Co2 is the green house gas, not the oil in the exhaust. That is a different pollution issue
Electric, unless you have a specific task.... like silent trolling.... waste of time and money as an outboard.
4 stroke is quieter and smoother running. But all the opposite to the 2 stroke savings.
The Chinese outboards are mostly of two types. A copy of an old generation "name brand" outboard, or a cheap re hash of a cheap 2 stoke air cooled engine (weed eater engines are common) with a plastic outboard looking cowling around them.
Some have proven reliable and others have not. Like all Chinese, it seems to be a lottery as to which one you get.
Personally I would not go for a Cheap Chinese. I bought a little Merc 2Hp for $350. It starts first pull an runs sweet. You don't have to pay a heap for a decent second hand. Go see an outboard guy and see what they have for sale.