airline offers both the qr code and the boarding pass as a pdf (but I don't have a printer at home). I screenshot the qr code (front and backside) and downloaded the boarding pass to my phone. No services from google were used.

I screenshot the qr code three times because Im afraid quality won't be good enough and I still have to ask: Is the picture quality good enough for the kiosks? Do agents simply check if there is a qr code and the name of the airline and let you board? or do they scan the code?

I've been assigned a seat right before the wings in the middle of a 3 seat row. Is this a good seat? Because I've heard people prefer frontal seats (rows 1 to 15), because engine noise shouldn't be as loud and to choose a frontal seat is more expensive than a seat at the back. I'm not really convinced, because if you have a seat at the end of the plane, you are among the first to leave the plane. Being next to the wings means you have to fight other passengers to board and leave the plane. Is really that calmer at the front side?

Have you ever deliberately checked in physically to get a free window seat? A friend of mine did that and he got it.