It's occasionally mentioned, but the answer appears to be "roughly 1000x current global electricity production", so we don't worry about it too much. Energy is much higher than electricity, of course, but we're not planning on replacing all energy [or all electricity] with just wind.

We'll hit other constraints long before that happens.

There may be some local effects. I think the main one is one cluster of wind turbines effecting the output of nearby clusters (and effects within a cluster). Pretty sure they account for this when engineering wind farms, with the effects actively being studied.

Probably a lot: https://pmc.ncbi.nlm.nih.gov/articles/PMC526278/