I think the difference between 34mm working with Omega and not with ROLEX could be due to thickness? I have a vintage 1940s 34mm Omega (actually under 34mm, I think it's 33.8 or so) and I used to feel like this is too small when I first purchased it. But lately I've been digging smaller watches. I tried it on the other day and it felt so right. It's a thin watch at under 8mm. I think that's why it works so well. Alternatively, I have a 38mm Seiko SKX that is just so thick that I can't stand to wear it, even though technically 38mm typically works well on my wrist... probably the sweet spot. Having a bezel makes it wear even smaller.
Aside from my 3861 Speedmaster (which wears fairly big, but I just love it), my most worn watch lately is a vintage Seiko that is 36mm and 8mm thick, lug to lug of 43mm. It's all dial and wears perfectly at that size for my wrist.
I'm not sure what the thickness of the 34mm Rolex are, but I would guess they are thicker than the vintage Constellations and such. On a side note, I would LOVE to have a vintage Constellation.