You can see the info if you go to Tactics->Analysis->Tactics->Tactics faced
Retain Possession is like selecting shorter passing and Fewer risky passes on your team. I never really use that shout, I'm playing as Leeds and I have a lot of players who are average passers but don't have the best vision or decisions stats.
I don't use any of the team instructions I just manually set all of the positions to shorter passing, my central midfielders and defence are all set to less risky passes as well, then I have Sam Saiz (or Pablo Hernandez) as my number 10 (as a Trequartista who has more direct passing and more risky passes, basically he is the creative hub for the team, the rest of the team is basically set to just get him the ball, then when he gets it his focus is solely to unlock the door, whether thats whipping out to my wingers in space or a through ball to Lasogga in front
It works ok for me so far, if he is getting marked out of the game then the less risky passes on the other players means they don't keep searching for him and we keep the ball and just recycle it until there's a crossing opportunity
Might not necessarily work for you but the way I look at it is team instructions can be overrated as they also encourage players who aren't comfortable on the ball to hold on to it until there's a chance for an safe pass, but it also limits your flair players to playing in a restricted way too or players with low work rate and aggression to close down all the time which just doesn't suit them.
Player instructions are my favoured way of setting up teams but it's probably more time consuming so just depends what you're wanting to achieve in the game