I have three females in a 2x4. Not the biggest because my living room isn't really big enough for a larger cage. We're looking now to buying a house so I will have space for more piggers, woohoo! Mine are very able to do laps in the cage, but I let them out for floor time in the bedroom daily. Bonnie is becoming more of a lap pig in her old age (1.5 years!).
The biggest issue I have is really toilet training. I had it down to a T when I just had Bonnie and Bramble. Bonnie has always used the litter tray for everything. When I first got Bramble, she copied Bonnie within a week at the tender age of 6 weeks old. However, when I got Lucy in December, everything went to pot(ty). Bonnie is still very reliable, however since Lucy has no desire to 'go' in the tray, Bramble has given up too. Bramble poos where Lucy does - i.e. all over the place. So, I've just kept some hay in there to encourage them to go in it.
Lucy was fine during quarantining. I kept them in seperate rooms for nearly 2 weeks and then moved Lucy into the same room where she could smell the others. She is a bit of a bully but introductions went well and they all live together peacefully, except during occasional bouts of PMS. I have a good mix of personalities - Bonnie is very large (1.25kg) but very submissive. Bramble is just a clown, she is just daft. She sticks up for herself but generally just bumbles along. She is now just over 6 months old so is not quite fully grown at 900g. Lucy (very small in comparison to the other two at 890g) was either injured or bitten severely when she was young. Both her ears are very torn and she clearly has her own 'territory' in the cage. She is very possessive of food and I need to have three food bowls for a peaceful existence. This is something you might need to consider having space for.