I also wonder what would be the relationship between OVF and the optical lens.
To each his own. For me, I would disagree on most points. Optical viewfinder is just as much an asset indoors in low light where the lcd really degrades. LCD still has the built in lag only showing you what recently happened, but you can't photograph it because it's too late. And available light works for special artsy, moody things and for special effects, but if you want sharp clear images indoors in lower or even typical lighting, flash is an absolute necessity. Image quality won't be in the same category without flash.
There should be no perceptible effect on the brightness of the lens -- the WA adapter is an afocal lens and doesn't change the aperture values. There may be a very slight decrease because you've added some additional lens surfaces but, if the lens is multi-coated, that loss will be less than 1 percent. Wide angle adapters can result in some additional distortion in some cases -- it depends on how well the WA lens is matched to the camera lens.
I know nothing about an AMOLED screen as I have never owned one and base my opinions on my experiences, but can guarantee you that the lag on the lcd of cameras is not imperceptible. Anyone can easily prove this to themselves by trying a few really simple experiments. Set up a 2 year old at close range with a piece of chocolate cake, prefocus to take the focus lag away, watch your lcd only and try to catch that perfect expression. Then if you have a way, use the same camera using the optical viewfinder or just looking over the camera not watching the lcd. In the first instance be prepared to throw lots of shots of the kid's ears, chin, hands in front of face, etc away and have a few good ones. With the second trial enjoy your well timed shots.
