Does the tempo you run affect the other team also? I've read where admin says no, but a lot of players say yes. How can players know better than the people who created the game?

The true answer is sort of.  It does not affect the other team, except that it does make them have more possessions, which will result in more fatigue on their part. 

So if you play normal tempoo vs. a uptempto team, you will have more fatigue than if you played vs. the same team going slowdown.  But you ave possession length would be the same, and it doesn't affect yourFG% or anything (at least if you controlled for the fatigue affect). 

So going uptempo does indirectly affect the other team via fatigue, but it won't make them play faster or anything

ok. that makes sense. thank you.

The verdict for me is that there are several Fatigue/Stamina theads and posts ongoing.  How many articles irl mention stamina or fatigue when previewing a rl game or in the game summary?  That should tell you something right there.