The limits that you may notice with copper such as the distance or quality of the copper pair are no longer applicable with fiber: optical fiber cables are impervious to electromagnetic interference—it’s virtually noise-free—and experience far less signal loss when traveling over distance. The speeds will only depend on the package you choose, and you will get full capacity right after line activation.
It’s very unlikely you will experience any speed issues with your fiber connection, but if you do, first ensure that your local network is gigabit-compatible.