Speed reading doesn't really exist. What exists is 1. some people read a bit faster than others and 2. skipping words. Number 2 is the thing that makes a "spead reader". Highly redundant writing is good for "spead reading", math papers not so much.
Multitasking doesn't really exist, aside from repetitive simple movements. So it's a bad idea to play any game that isn't a dumb grind, but then why play that in the first place? Doing simple chores and exercises while listening is OK.