Hi I would recommend stitching the collars together, I would never buy a collar that isn’t stitched. I see stitching on collars and leads as a sign of strength Iv had to many collars that have been held together by those metal studs and have ended up failing when put under pressure. And use good quality brass or bronze D rings as iv also had cheap collars with low quality metal D rings crack or split when a strong dog pulls! Hope this helps
Good luck
David