How many pages/screens are included in the project?

The discovery and definition phase of the project will uncover the users main objectives, and there will be a core series of screens that allow the user to achieve those objectives from their initial landing page: this set of screens should be as short as possible for a better UX. Usually these flows will be around 4 screens long.

How many flows are included?

From the initial studies of personas there are usually around three to five core user needs, or motivations, from which flows are derived. Oftentimes there are shorter supporting flows to enable to user to follow those flows: such as login and sign up, or frequently asked questions, etc.

How many meetings will we need?

There are a series of initial meetings during the content workshops phase: the number depends but usually around 2-4 meetings are enough to gather the information for a scope definition. Then there are checkpoint meetings around each phase, often for iterative tweaking.

Which device size should I choose as default?

If your users are to be engaged mainly through a mobile, then that should clearly be the default option - and this is the default design option. However, if your UI is complex (eg. enterprise scale complexity) and is used mainly through desktop computers, then it may be better to start at desktop scale and consider making it responsive to mobile as a secondary option.