Need help designing a parallel sandbox campaign.

[BrotherBen]

At some point in the future I may end up running a campaign for 2 groups. To complicate things I also prefer running homebrew campaigns and not mods. Instead of running a campaign for each of the groups I thought I'd write one set of material for both groups. I have issues concerning how the two groups could interact, but I'd rather examine them myself for now. The main issue with balance I have is that one group consists of 3-4 players and the other consists of 6-8. I could simply adjust the CR between groups, but I'm always looking for more creative solutions.

Since this won't happen for another year or so, I have plenty of time.

[Crimson Jester]

Have you thought of running them at differing times? So group A was here 50 years in the past.

[Grimmy]

Some ideas in here

[Lightbulb]

I would have them always just miss each other - and not often. Or hear rumours of each others exploits.

Wouldn't run they through the same adventure.

More two groups in the same world than parallel worlds. Especially since if you run it sandbox they will diverge further and further and time goes on meaning you will have to do the prep twice anyway.