One thing to consider is if you have fields that are required. You can do a test to confirm if I have this right, but In my experience, if certain fields are labelled as required and you hide them in your publish layout for a channel, you get a “mystery” error when you submit the entry.
For example, if you have one field group to use among two channels called Pets and Friends:
- Pet Name (required)
- Pet Status
- Friend’s Name (required)
- Friend’s Status
And in the publish layout for Pets you have:
- Pet name (required)
- Pet status
- HIDDEN -> Friend’s Name (required)
- HIDDEN -> Friend’s Status
Now, when you submit an entry for a pet, it will throw an error and require Friend’s Name be filled out.
But wait, it’s hidden, you cannot fill it out and don’t even know what the error is for, because—it’s hidden!
So either have no required fields or else break up into multiple smaller field groups (which is what I ended up doing).