For office networks, CAT 5e cable is usually enough, especially if you do not plan on extremely high loads. As you correctly noted,
cat 5e speed is up to 1 Gbps, which is enough for most tasks. But if you plan on future improvements or connecting devices that may require more bandwidth, it is better to choose CAT 6. It supports speeds up to 10 Gbps and is less susceptible to interference, especially over long distances. It is also worth considering the maximum cable length - for CAT 5e it usually does not exceed 100 meters. If the length is longer, it is better to think about higher-speed options.