Its one step to use LrC to import photos to SSD, its two steps to load pics onto SSD and then import
Catalogs can be stored anywhere that you have write permission, and then the photos will reflect changes in LrC only when viewed in LrC. The original images (no matter where you store them) are never changed by LrC.
Definitely NOT, especially for beginners. Use one catalog for all photos, and organize within the catalog by metadata
Lightroom is designed as a one stop shop for most photographers. It can import directly from a card, and also does file integrity checking as it imports. For speed, the catalog is best kept on the main drive. This also means that you can still do a certain amount of work if the photo SSD is disconnected. Lightroom is designed with one large catalog in mind for better access to image search and for syncing online. You can use collections to manage different shoots.
Sean McCormack. Author. Magazine Writer. Former Official Fuji X-Photographer.