The right saddle for touring
The best kind of saddle for touring is one which you find comfortable.

The cut-out is intended to relieve pressure from your soft bits leaving most of your weight on your sit-bones.

A very wide saddle might start to rub excessively inside your thigh on a long ride, while one with springs may be too bouncy at higher cadences and waste some of your effort.

A saddle is a personal choice and there is certainly no one ideal, "best" touring saddle for all people.

Given that you "love" your Brooks, I'd suggest looking at another Brooks (maybe a narrower one), or if you're confident it will be comfortable over longer distances, use your B66.