Dell's specifications for the 5620 with NVIDIA GeForce RTX 2050 and 5620 with NVIDIA GeForce MX570/570A state that the system supports only a single drive. You are not limited to 1 TB. You may replace that drive with a larger drive, all the way up to 4 TB. Whenever touching components or working inside a computer, wear a grounded wrist strap, also called anti-static wrist strap, ESD wrist strap, or ground bracelet. It's a cheap and sensible precaution. Rest the laptop on an anti-static mat or at least a reasonable alternative such as corrugated cardboard. (Repeatedly touching a metal case part is not sufficient mitigation with modern components.)
I am interested in purchasing a 5620 which already comes with a 1TB SSD. Can an additional SSD be added? If so, what are the best options?
Dell 16" 5620 - Dual SSDS