Multiple Gateways on Multiple devices

When you create a Standard/Enterprise gateway you have the option of creating a gateway cluster.  This is highly recommended for Business Continuity reasons.

Independently, a dataset's on-premise data sources must all be served by the same gateway cluster.  That limitation will dictate if you can make do with one cluster, or if you need multiple clusters.

Independently, the connection type has a big impact on your gateway design.  Direct Query connections require a very fast network interface, but don't need much memory or disk space.  Import Mode connections require lots of memory, disk space, and CPU capacity.  That means it may be sometimes better to have separate gateway clusters for Direct Query (and Power Platform)  and others dedicated to Import mode.

If you have multiple gateways and gateway cluster members then your maintenance effort (drivers, updates, monitoring etc) will increase.