Some of the stereotypes about Sunday football are fair, some are wildly outdated and some vary from league to league and up and down the divisions.
My personal opinion is that a lot of the stereotypes aren't really that relevant any more. Specifically at low levels, the deciding factor on if a team plays Saturday or Sunday isn't when they want to go drinking, or if they want to fight or not, it's down to when they have free time. So you'll get Sunday teams that are good as gold and only play Sunday because some of them work/play semi-pro Saturdays, and you'll have Saturday teams who are up for a fight but happen to play Saturdays because that's when a pitch is free or that's when their partners can look after the kids.
I'm not someone who likes to do "research" pre-match, so I turn up to my Saturday games with an open mind, see what mood the players are in, how seriously they take their warm ups, what the first few tackles are like and go from there. That method works perfectly well for me, Saturdays or Sundays, up and down the levels. Sometimes Sunday teams just want to have a kick about, and if you're turning up every time expecting World War 3, you can end up becoming an obstacle to enjoyment and part of the problem.
If they're playing in the right spirit, let them. If they're not, get involved. And that applies regardless of which day the match is happening on.