does it matter for street?
I guess not. I was mainly wondering for flat.
Yes.
Depends of the rider.
i have knee problems too. it affects my drops but i just cant seem to get as good at flat i dont know why. i cant commit to spins and my feet dont seem to like to come off and go back on the pedals 
for now im just wearing knee braces when i ride (untill my knees say enough)
True.
Now I’m confused.
wouldnt matter for me cause i dont do tricks where i use to crown of my frame:D
Is it a whole new frame or just a gusset on both sides? Like the color.