I'm running Nextcloud on a shared webhosting and have mounted a Hetzner storage box as external storage into it. That comes down to around 7 €/month for hosting costs, which I find fair.

I'm using the Nextcloud Android client, which could be better but does its job, to sync photos from my phone to the cloud. That can also be configured quite nicely to have specific folders for uploads, that should help you with keeping stuff seperate with several devices.

I've no experience with the office suite to be honest, never really looked into that.

Using shared hosting will come with the benefit that you will, most likely, have custom TLD to run your mail from/to. Shared hosting also does regular backups without you taking care about that etc. etc.

I'd say you should get yourself a Hetzner "Level 4" shared webhosting for domain, mail and "root" of the Nextcloud and then mount a storage box into that. Should be around 9 €/month then.