Is there a certain area and font in which one would stencil their Duffel or Laundry bags? Is there any regulation indicating such?

This is really a Unit SOP. The stenciling is usually along the side so the the handle is on top. Many units also use the bottom of the bag as well. The unit SOP for the 101st was pretty standard, with a desert tan or white background. Cav units almost always do the red and white diagonal background with black lettering. Some units also have designated shapes/rings of different colors so you can tell a first Platoon B Co from a Third Platoon C Co bag apart. Despite all this, people's stuff gets lost and misrouted.

The letters were like an inch and a half high
Side:
Last Name, First Middle Initial
Rank
Unit

Bottom
Last Name, First Initial
Rank
Unit


You need to be careful, if your unit SOP is to not stencil and paint, they'll make you pay for the duffelbag.

I can't vouch for this company, but they must have gotten the 4BCT 101st ABN stenciling SOP from their examples.

https://lombard.design/archives/997

Stencil it along the body of the duffel bag.

We used the manual stencil press with one-inch letters. Center it on the laundry bag, and I have never had a duffle bag with a zipper.