Eh. It's more important to be consistent and fair then dominant and strong with most dogs, even the working lines IMHO
Most pet owners I've met are very very inconsistent with their dogs. Forgetting to release after commands, not reinforcing ignored commands, constantly changing the rules.
My, albeit limited, experience with working dogs seems to be their are a plethora of personalities amongst them and to say all WL need a strong or dominant handler just doesn't fit. I've seen dogs that are so hard that practically need a 2x4 slammed over their head before they notice a correction. I've seen others that act like the world is ending if their person just gives a stern verbal. Some dogs shut down if given a correction too strong for it. Others will turn and lash out at their handlers for the unfair treatment. Most are somewhere in the middle.
If you are interested in a working line dog the most important thing is developing a good relationship with some breeders, owners, and trainers. There are going to be dogs out there to suit just about any handler's style, energy, experience level, and goals.
Getting to know people who work dogs regularly well help you find people producing dogs you will be best matched with.