Is it better on the engine running Planet Coaster to Group objects into a building vs creating many single pieces? Wondering if load times decrease when items are grouped. Does this have an effect in caching objects or anything?
I don't believe this has any effect on performance. The number of objects on your map will slow your load times and fps. If you build with less items, (and use less billboards, special effects, limit guest numbers, less glass items) you will get better performance regardless of whether they are single items or buildings.