It is very difficult to give a one-size-fits-all recommendation. Generally I try to keep as much as possible in a single doc, only splitting into separate docs for security reasons.
Here is a thread with quite a bit of detail:
As far as “trying out things” go, you can create a new page with the new layout in a hidden area, and then when everything is ready, make it visible to users. However, it will depend on how invasive the changes are that you want to make. If you are going to make changes to the structure of tables, remove fields, etc, then it may impact your existing layouts. But that would mostly apply to using Cross doc as well.
The best approach is to try out different scenarios with your specific setup and see how things work out before committing to a specific approach.
Gruesse aus Atlanta