If you’re considering cohabiting them in the same enclosure I’d recommend to reconsider. If you want to cohabit them I’d give this a thorough read.
If you’re cohabiting it will take more space for 2 much larger enclosures (each with a female and male and necessary to be bigger) than it will for 4 smaller enclosures for each individual.
If I misunderstood what you were asking and you’re not looking to cohabit I know some good sizes are:
Racks- FB70
Tubs- 28 qt if they don’t get to big
Aquariums- 25 gallon
I don’t know a whole lot about BPs nor do I have experience with them so I’ll let someone else chime in if they have better size recommendations.