Confirmed in F on A320s and 757s over the next few days - but inexperienced with NW.

(1) How much prior to published departure times does actual boarding commence (in the normal course of things) - SFO / MSP / TPA ?

(2) How good/bad is the overhead bin situation in both the 320s and 757s in F? Do I need to wave my boarding pass, shout "do you know who I am and where I'm sitting " while wheeling over the backs of several feet to make sure my normal bag gets overhead? Or is there generally enough F space for all / almost all. (Also, do they reserve any special bin for row 1?)

Thanks!