The aim of a neighbourhood plan would be for local people to have some say and control over what is built in Marple @Russ . Without it, and maybe even with it, Marple will otherwise get what it is allocated and will have no say in the matter. So it will surely be better to have a plan rather than not to? I would expect a Neighbourhood Plan to address issues like traffic and highlight problem areas like you are concerned about.
As I understand it, Marple will get what it is allocated, regardless of anything people here want. The neighbourhood plan can include extra housing over and above what is allocated, but cannot reject housing which the council wants to build. This is clear both from the legislation and also from the preambles to existing neighbourhood plans which make clear there is no real choice. All the plan can do is choose to a certain extent where things get built and not stop unnecessary and damaging development.
Once the plan, with all the develoment people don't want but can't stop, is approved, the council and goverment can say 'well, you supported it', depite the plan being nothing like the plan the people here actually want, because the plan is not about letting local people decide what to do.
For a neighbourhood plan to mean anything, it must allow local people to make decisions which do not have to match what the council or government have decided. Otherwise, it is meaningless and a fraud.