Irrespective of whether you start working for them with a work permit or not, and irrespective of whether you have a job offer or not, if you score enough points and get PR through express entry, you are free to move wherever/whenever you want.
If you go through PNP, you are locked into the province (not the employer) for some period of time. However, I don’t know how well it is enforced. It’s more like you’re expected to stay in that province since they nominated you, and must have a good reason (e.g. not able to find job in that province) to move out.
Check whether EE requires LMIA for your job offer (if you don’t already have it). If you score enough points then I would recommend EE over PNP as it gives you a lot more freedom to move immediately.