Would a combined malar submalar implant or extended orbital rim-malar implant be best for my very concave middle face? (photos)

I will need to see better photos.  As you have described one wants to "Fill" the flat area only and the ways to do this are many; each with advantages and disadvantages. Face forward and profile photos are preferred for evaluation.

it is very difficult to comment without actually seeing you from frontit also matters what you want projection or width or both 

What you are seeking is augmentation of the anterior malar region that also extends onto the lateral orbital rim and into the submalar region. Ideally a custom made implant is the best way to approach this unique area of midface augmentation. But certain styles of combined malar-submalar implants can be modified to closely approximate the ideal shape. Any form of orbital rim implant does not provide enough volume to the submalar region to be effective for this type of result.

Hi there. Is that you in the picture alongside the model? It would really help to have a full front and side views of your face in order to reach a conclusion about what would suit your face best. In case you have under eye hollows an extended orbitomalar implant will be better. However everyones facial structure is different and every patients needs are also different. Please consult a PS. 

Yes, you would benefit from softer, fuller, rounder cheeks.  This look makes women more beautiful and  feminine.  While your photos are not great quality, I can see that adding fullness to the cheek area would softer your face.  If you would like to send better photos, we can evaluate them.