One question, answered from the books
How do I close a won game in League of Legends?
Stop taking things and go win. When you're ahead, the game should get less exciting, not more: convert the next won fight into Baron or an inhibitor instead of a chase, split the map so they defend two doors at once, reset before the throw window opens, and never take a fight where losing costs your Nexus. The lead was the hard part. Closing is doing obvious things in the right order while bored, and the players who can't stand the boredom are the ones who keep games close on purpose.
The decision, as a picture
What it looks like in a real game
Five thousand gold up at twenty minutes, and mid just died mispositioning for a pick nobody priced. Ten minutes later the gold graph is even and your team is asking how. Nobody threw in one play; the lead got spent one coinflip at a time. The disciplined version of that game is duller and shorter: won fight, count the dead, Baron, two inhibitors, out before the respawns, end on the next objective. Same players, same champions, ten fewer chances to lose.
The concept: the closing script
Boring Wins treats closing as a script you run, and the script exists so you don't have to be creative with a lead. Creativity is what losing teams need; winning teams need order. Count the dead before you commit to anything. Prefer structures to kills, because towers and inhibitors don't respawn and shutdowns do. And leave while it still feels early, since the throw window opens exactly one fight after the fight you should have left on.
"The closing script: count the dead, end or Baron, split, two inhibitors, out, next objective, end."
"Closing looks boring when done right. Boring wins."