I mean, it's pretty accurate that a bunch of regulars are chilling when you trying to close up lol

When you stay up passed 9 with the lights on, does that cost extra or does it not count? (I mean for the electric bill)

I never thought about it. So evident, still I didn't thought about it!

After closing and doing restocking and pack openings I have around 3 people sitting at different tables

I will say this was useful because in my playthrough, some nights there were solitary customers waiting for a game at close. Unlike those who actually found playing partners, these solitary customers would never leave of their own volition; they would simply sit at the table forever, waiting for a playing partner that would never come. I would at least wait until everyone else had left before kicking out one of these solitary stragglers with Q.

So you can just wait a minute or two for the tournament players to finish instead of kicking them out with Q. If you kick them out with Q and you've already flipped your sign to "closed", then it's almost 100% likely that the customers will immediately leave the store (unless they still have goods they haven't bought yet).

If instead, you wait for them to finish their game, then there's a chance that they'll continue to shop (even if your sign says "closed", since they were there before you closed the shop) and they can still buy things. I had one after-hours tournament of 6 different people end once and 5 of them ended up continuing to shop and even though it was after 9;00 p.m., I still made about $400 from those people since they each bought about $80 worth of stuff.

But yeah, if you kick them out with Q, then they're pretty much certainly just going to leave (again, unless they picked up stuff to buy later before they sat down at the table).