As you can see by my
post these types of posts typically dont get too many answers because there are so many theories and EA has never told any of us exactly what sliders affect other than just what their 5 word sentence says.
Reaction time typically refers to how quickly the secondary defensive player moves or changes direction based on what the offensive player is doing. Think of it as a funnel, if the slider is lower there is a lot more open space because the defensive player is reacting slower, the higher the number the smaller the open space because the defensive player is reacting on par to the offensive player.
And putting it to 100 doesnt mean they will cover perfectly all the time, its all a dice roll, it will increase or decrease the chances that dice roll will go your way.
Blocking is typically how long a player will hold their block. Now I can go into all of the hidden blocking slider talk but I dont want to over load you. If the # is lower they wont hold their block as long, if higher will hold it longer and there will be more time for you to run.
As you can see yours and my post have about 400 views with not many replies just becuase there are so many theories and placebo effects it can be a challenge to get correct info. Ive been on the OS forums for almost 20 years (yes im old) and that is just how it goes. Now that you have a reply others should post as well. But I will tell you OS has wasily the most information related to sliders, now not all of it is spot on but there are people on here who have dedicated years to figuring out what EA wont tell us for the love of the sports game and trying to turn it into the sim we all want.