Picking the wrong shape of machine is a more expensive mistake than picking the wrong size, so it is worth understanding the three classes.
Performance
Highest clock speed, fewer cores. The right choice for game hosting, where each server is bottlenecked on a single tick thread and clock speed is what you feel.
Capacity
More cores and more memory at a lower clock. The right choice for virtualisation, container hosts and panel nodes running many independent things at once.
Storage
Capacity-first disk configuration. The right choice for backup targets, archives and data-heavy services where disk space rather than compute is the constraint.
A high core count server is often the wrong choice for game hosting, even though the spec sheet looks more impressive. Games cannot use the cores.