so since I saw people discussing FPS and shadows and lag or what-not, I decided to do something myself to see how my computer performed.
229993 bricks
(the map was a recreation of slopes that Treynolds416 made with a script, and yes you read that right 229k bricks)
max view distance
no shadows: 60 FPS
minimum: 60 FPS
low: 60 FPS
medium: 60 FPS
high: 50-57 FPS
on very high/max, no shadows appeared at all .. weird.
keep in mind this was all in single player.