From my research, it seems that Cat Ba is what I want to see, more so than typical Halong Bay. Am I wrong?
I don't remember being in Cat Ba. We did a 2 days Halong Bay cruise. It was absolutely gorgeous.
La Pinta Luxury Cruise, Halong Bay - Lan Ha Bay
I reserved it through Expedia. Expedia had some spending promotion at the time. But they just send it to a local agency:
Le Thanh Son
ODC Travel Company
Tour Operator
43 Hang Bo St, Hoan Kiem Disc, Hanoi - Vietnam.
My whatsapp: +84916.069.069
Tel: 84.24.39232324
Fax: 84.24.39231510
email: thanhson@odctravel.com.vn
The staff on the boat was very accommodating with our dietary restrictions and was very nice in general.