Yes, and the economic reasoning behind this is as follows: The plague wiped out a large proportion of the population. This made labor more scarce while the amount of capital (read land and animals) remained roughly the same. You need both capital and labor to produce (called complementaries in economics) and the relative abundance of each determines their price, or in the case of a laborer, how much they are paid.

TLDR: same amount of land, fewer people to work it, those people ask more money.

There will be historians here who can probably provide actual evidence of higher wages. You are also likely to see political shifts as a consequence of this, so peasant's rights and the like for example, but I'll leave that to a specialist.

To a certain extent, yes. But this argument has been taken to extremes at times, claiming that the poor were able to acquire "wealth" so to speak. This is in part due to Boccaccio's Decameron, which historians now generally agree is exaggerated for the sake of literature. Workers may have gained bargaining power, but they were not quickly escalating up the social ladder. There were ordinances passed to control wages, too. The upper classes were not dumb and knew this could be a major consequence of the plague. Check out Aberth's book on the BD and Horrox's, too. There is an entire section entitled "Consequences" that discusses just that through primary sources.