They are actually different cases:
In the case of proved/proven, both your sentences are simply a present perfect. The thing is that proved and proven are both accepted as participles for prove.
Just make sure you do not use both of them in the same text, as a matter of consistency.
As for light-weight versus light-weighted, weight is a noun in the first case, used as an adjective in combination with light. In the second case, you have the participle of the verb weight, also used as an adjective.
In this case there is a difference in meaning as well: the common expression is light-weight, meaning that is is not heavy.
Light-weighted however implies that someone has weighted it, meaning that weight was deliberately added, but not much (as it was done lightly). Usually that is not the implication that is meant :)