Yes, that’s not much. Especially then it is very important to tune the parameters of all services.
You could though use a Raspberry or similar device only for Nextcloud and connect to your NAS storage. However, a 64-bit system would be nice (not sure what the state of the Linux images for RPi 3 is and if they are already on 64 bit). Advantage: you have a default Linux and can directly follow the guides.