Downloads won't be rough at 500mbps
You could theoretically download a 25gb 4k bluray movie in 7 minutes , then it would take 90 minutes to watch it
Unlikely going to a gig would be any faster as you'd need a server capable of more
I am a tech guy who lives alone and I pay for 35 for 200. Gig is available but it just wouldn't make any difference beyond occasionally downloading a brand new 100gb video game. But I don't do that often so an extra ten minutes is rather meaningless
As long as your access point isn't also a dhcp server you shouldn't have to do any of that
1.2 or 2.1 should both work. If you use 1.2 make sure your router isn't starting the address pool that low
What ip are your devices getting from dhcp