You can totally print snap-fit connectors for 3D printing, but you need to keep some things in mind. I assume that since you have looked at these connectors, you have a good idea about the matter, but I nevertheless suggest Angus (MakersMuse) discussion locking devices at the beginning of a tutorial Video on designing buckles.
Your tabs thickness will need to be at least one line width wide at the most narrow point to be printable at all.
Another thing besides thickness is orientation. For the strongest tabs, you might want to print the tabs like a C for maximum part strength. Just modeling the part with the tabs, it should print in this orientation then:
This way the bending is not applying stress against layer boundaries but 90° to them, giving even force on each layer. This means that you will need to print parts in awkward orientations just for the tabs usually. You will need lots of support.
You can certainly print in a less awkward position at the expense of strength of the tab, acknowledging that "this is a prototype, we can show you that it closes perfectly like this, though due to FDM limitations we might break the tabs opening it again. So we'll be careful."
prototype-variation of model
It might be however easier to print the tabs flat and without the hooks, allowing to do a fitting test, but not a snap-connection. Your benefit is, that you won't have to watch for print orientation, but it won't be locking. Make sure to work with workflow and put the modifications for easy printing/not-locking at the end. Alterations to the general design should come all before this point. Then turn off these steps to create the model that is sent to machining for the mold.
Modular intermediate design
If you need to have working, strong tabs AND a good print, it can pay off to print separate parts that combine into a single piece with a little glue. Maybe the C-clamp is actually a thin bar that is put into the back plate and glued into place or secured with a little friction weld.