Filesets: splitting a huge directory

greetings, happy new year to everyone!

I have a FAQ, I assume, but my googling and RTFM didn't help me so far, 
sorry.

At a customer I have to set up various Jobs to backup a huge directory 
with movies. I want to split that into several smaller jobs by using 
Filesets.

So I asked an LLM:

# this should backup only files and directories
# starting with "a-g" or "A-G"

Fileset {
   Name = "films-A-G"
   Include {
     File = "/data/multimedia/films"
     Options {
       Regex = ".*/[A-Ga-g][^/]*$"
     }
   }
}

That doesn't seem to work, and more or less looks wrong to me.

What's the way to go here?

Regex? Wildfile? WildDir?

trial and error is a bit problematic, as these jobs are terabytes in 
size quickly.

Do I remember correctly that someone posted some test-script for such cases?

thanks in advance ...