Ball Race has 7 different payouts and most of them require 2 or more players to be awarded

Collected X Melons
- You can get 40 units per melon collected, there's a cap of 60 melons for this payout. (*)

Didn't Die
- You get 200 units by completing a stage without losing any life.

1st Place (4+ Players)
- Clear the stage in first place to get 750 units.

2nd Place (4+ Players)
- Clear the stage in second place to get 500 units.

3rd Place (4+ Players)
- Clear the stage in third place to get 300 units.

4th Place and Below (4+ Players)
- Clear the stage in any place below 3rd to get 150 units.

Team Player (2+ Players)
- You get 500 units if you press a button that blocks a path in any level.

Collected 10 melons (Very Hard) = 520 Units
1st Place (Very Hard) = 975 units
Team Player (Very Hard) = 650 units

520 + 975 + 650 = 2,145 Units
2,145 x 1.5 = 3,218 EXP

- I personally recommend getting as many melons you can during the bonus stages, don't bother getting more than 40 melons cause you won't get extra units if you collect more than 40.

- As recommended by one of the ball race expert players, Nimbus is the recommended map to get fast EXP.

(*) Payout text is not updated but they upped the payouts for the melons.

Minigolf has 11 different payouts and are based on how you perform on each hole.

Hole In One!
- Awards 800 Units if you putt the ball in one stroke, most of the holes that can be done in one stroke will also grant and achievement plus 1,500 units.

Phoenix
- Grants 900 Units if you putt the ball 6 strokes below par, this payout is really rare.

Flamingo
- Grants 800 Units if you putt the ball 5 strokes below par.

Condor
- Grants 700 Units if you putt the ball 4 strokes below par.

Albatross
- Grants 600 units if you putt the ball 3 strokes below par. Get 10 of these to unlock the "Ancient Mariner" achievement and extra 25,000 units.

Eagle
- Grants 500 units if you putt the ball 2 strokes below par. Get 25 of these to unlock the "Screaming Eagles" achievement and extra 10,000 units.

Birdie
- Grants 400 units if you putt the ball 1 stroke below par. Get 50 of these to unlock the "Green Greens" achievement and extra 1,500 units.

Par
- Grants 300 units if you putt the ball in the specified amount of strokes in each hole.

Bogey
- Grants 200 units if you putt the ball 1 stroke above par.

Double Bogey
- Grants 150 units if you putt the ball 2 strokes above par.

Over Double Bogey
- Grants 100 units if you putt the ball 3 or more strokes above par.

I personally recommend playing Mushroom Wood as they have a lot of easy HIOs, I am do recommend checking this guide here.

Zombie Massacre has 7 different payouts and these can be stacked per stage

Survived the Day
Awards 200 Units if you successfully survive a Day, this is basically the same thing as Thanks For Playing

Defeated the Boss
Awards 1,000 Units if you defeat The Queen on Day 6

Boss Destroyer (4+ Players)
Awards 500 Units for being the player that dealt more damage to The Queen

Boss Master (4+ Players)
Awards 400 Units for being the second player that dealt more damage to The Queen

Boss Handler (4+ Players)
Awards 300 Units for being the third player that dealt more damage to The Queen

Boss Helper (4+ Players)
Awards 250 Units for dealing damage to The Queen

Total Points
Awards X Units based on the points you scored during the day divided by 3

Thanks For Playing (Medium): 220
Survived The Day (Medium): 220
Total Points (Medium): 2,461

220 + 220 + 2,461 = 2,901
2,901 x 1.5 = 4,352 EXP

- I do recommend playing as either the Survivor, Electrician or the Mercenary (Preferably the latter two as the special item covering a large area)

- Gasoline imo is the best map you can play to get a bunch of EXP. If you survive the whole 6 days, you can get up to 24,000+ EXP per game.

(*) This section might be edited to add more information

Accelerate has 10 different payouts and these will require 2 or more players in order to be awarded.

1st Place
Awards 1,500 Units for ending the race in 1st place

2nd Place
Awards 1,200 Units for ending the race in 2nd place

3rd Place
Awards 800 Units for ending the race in 3rd place

4th Place and Below
Awards 600 Units for ending the race in 4th place and below

X Items Hit Other Players
You get 50 Units for every player you hit with the Items

Best Lap of the Game
Gives 200 Units if you get the fastest lap of the whole race

Gold Trophy
Gives 2,000 Units for being first on the leaderboard when the race ends

Silver Trophy
Gives 1,600 Units for being second on the leaderboard when the race ends

Bronze Trophy
Gives 1,200 Units for being third on the leaderboard when the race ends

Tincan Trophy
Gives 800 Units for being fourth or below on the leaderboard when the race ends

Thanks for Playing (Hard) = 250
First Place (Hard) = 1,500

+

Thanks for Playing (Hard) = 250
Gold Trophy (Hard) = 2,500
5 Items Hit Other Players (Hard) = 313
Best Lap of the Game (Hard) = 250

1,750 x 1.5 = 2,625 EXP
3,313 x 1.5 = 4,967 EXP

I definetly recommend playing this game mode with your friends, try to choose the maps with a higher difficulty as they will pay more units and therefore more EXP.