The latest high-end SSDs provide astonishing performance but for most users, a far more modest SSD will suffice. Any drive that can consistently provide close to 500MB/s read and write speeds will likely suit your needs.
What form factor?
SSDs come in a variety of form factors but the two main choices these days are 2.5-inch SATA drives or M.2 drives. The former are larger but cheaper, and come in higher capacities. The latter are tiny, and can provide the highest performance.
SATA or NVMe?
M.2 SSDs can run in one of two modes: NVMe or SATA. SATA versions are limited to the same ~550MB/s speed limit as 2.5-inch SATA drives. NVMe versions can go much, much faster.