on a personal cloud you rarely do load balancing. The deployment recommendations speak of 150 users and more than 10 TB of storage:
https://docs.nextcloud.com/server/12/admin_manual/installation/deployment_recommendations.html#mid-sized-enterprises
I would take this example and slowly add new features. First: Single webserver with separate DB server and storage server. Next step add a second webserver, then try a load balancer, …
If you have all the data on external storage, it shouldn’t be required to sync webserver files via syncthing.
If you don’t need one large setup, you could run several small instances. They are easier to maintain, you can keep them in individual vservers which makes it easy to move them around. To upgrade them, takes a bit more time because you have to do it on every instance separately but you can roll out new versions slowly and in case of problems it’s easier to restore than a very large setup.
@JasonBayton did some tests on clusters: