You need a business idea and model first, but as soon as you grasp it, you should sit down to plan both design and engineering at the same time. There are no benefits of delegating these responsibilities to separate team.
Our design team are a unique combination of talent and, creative thinking with analytical verification of artistic ideas. We try to involve all the stakeholders at the earliest stage of the design process.
Understanding the business and marketing plan helps the designers find the right balance in how the design works on web and mobile. That's why it's best if Your product manager starts planning with a scoping session with both the design and software development teams.
We put pressure on the UX design as well as the user interface in our products.