What's going to go over best is definitely going to depend on what your players like. If they get into your narrations, then 1 will work great. I'd avoid 2 and 3 just because they may just feel bad in practice, again depending on your group. I think 5 is my favorite, it can give the other players the chance to really hang it up if they're into that!
Wow that does sound like a challenge to balance for! Here's a few things to keep in mind.
A larger group of players is usually going to need more enemies for any given combat to be challenging. If you're using a prewritten adventure or an encounter builder of some sort, consider bumping up the number of monsters a little.
Consider alternate objectives/fail states. This can take some creativity to pull off, but introducing something like hostages in danger, or a thief trying to carry away some of the party's loot during combat can make things much more interesting. This can be especially effective with paladins, when what their oath says they should do conflicts with the tactically correct move.
When they can, enemies will want to create advantage before the fight even starts. Letting the players into sticky webs, slippery floors, or a prepared portcullis can restrict their movement and create openings to attack. They might also try to break or disarm weapons or shields when they see the paladins are hard to hit head on.
It's good for the players to feel powerful! Most encounters should be challenging, and the players should occasionally be pushed to their limits in a boss fight, but a few cakewalk encounters are good to have too. They're especially good when they're similar to a fight the players had a lot of trouble with 3 or 4 levels ago to highlight just how strong the characters have become.
I'm the same way, but mine is "Toxic" also by Brittany.