Well it is much easier and faster on the older kindles like the K3 where its just a hit on the menu button and then another click with the 5 way to turn wifi on or off.
It has bugged me all the time I have had the Paperwhite, mostly because its battery is so bad that I always had to keep wifi off or I barely made it through a day or a day and a half.
Now with the Voyage, I don't worry anymore. I can finally keep my wifi on and not worry about making it through a day. I get maybe 3 days out of it now. I do read a lot so I look at that as normal for my usage. I can read a book a day so that is why.
Since I like to look up stuff including dictionary and like to just keep my device synced all the time, I am really happy that I can leave wifi on now.
So I guess that takes care of #5 of the OP.
1. the light is even on my Voyage. I have had a really bad paperwhite 1 that had such uneven and splotchy lighting I didn't even use it anymore much. Read on my Fire6 at night. Now I am so happy with my Voyage I don't want to read on anything else. Its even, no dark splotches at the bottom, no diamond shaped light beams, no splotches. Just even.
2. I think my PW might have had a couple of reboots on its own after that big update, none of my other devices ever did. Not my Voyage so far either.
3. Light is not completely off I guess, no clue, I can't see it on the Voyage. I can't even see the lights on the bottom like I could on the Paperwhite. And with the auto light on I don't even think about the light anymore ever. I keep my light on lower then may though, I think inside highest is 10, mostly it hangs at 9. I'll only know when I check as its all automatic. outside it goes up to 14 as I trained it to do that. At night in bed it goes down to 8. And the screen never looks "lit" for lack of better word. It just looks like paper. I never see or notice any glow. I did notice that on my paperwhite.
4. e-ink screens have blinked since I had my first kindle in 2008 the K1. Back then there wasn't even an option to change to every 6 pages. I think the K3 still does every page also. I am on 6 pages with the Voyage as its so sharp that it doesn't deteriorate much at all by the time the "flash" comes up. I just don't notice that anymore after 7 years of reading on e-ink.