Clause 6.3 is about planning how to handle changes without breaking the quality management system. For example, when an organization moves to a new location or introduces a set of new production equipment it is necessary to plan the introduction of these changes in a controlled way. In your case, it could be the introduction of a new production line for sterile or wanting to get approval to export to South America a product developed for the European market. Both would require new procedures and practices.
Clause 8.1 is a general clause. Other clauses of section 8 have more precise references to changes. It can be, changes to planning, changes to the design, changes to raw materials, changes to people, changes to … For example, your production planning could be changed due to an urgent need in the market for a product currently out-of-stock.
Clause 8 .5.6 is about changes in the day-to-day of the organizations by the most varied reasons. For example, due to a delivery delay, your organization will use in production a raw material from a different supplier. Due to an equipment breakdown, production will be done at a different production line.
The following material will provide you more information about planning and controlling changes: