Some advices for new istallation

[cobra-arbok]

I have no experience with Zabbix and would like advice on how to install and configure it, especially where to install it.

I have to manage 5 small LANs which all have almost the same configuration: a ESXi Server; a Windows server; one or two Linux servers (Ubuntu and Debian); maximum 5 Windows 10 PCs; 2 Linux Xubuntu / Debian PCs; PfSense Firewall; a Qnap or Synology NAS; a FreeNAS / TrueNAS NAS; Guacamole for network access; OpenVPN for remote access.

I would like to manage the LANs centrally, but keeping them independent of each other.
Above all I want to manage:

1. the backup of PCs and Servers on a PC present in each LAN and to a Cloud service (Dropbox or OneDrive);
2. PC and Server updates through their respective update services;
3. managing antivirus.

I don't know if it is better to install Zabbix on a VPS on the Internet or on a server of mine in my LAN and connect the other LANs in VPN.

I haven't decided on a backup software yet, but I want to keep myself on an Open Source platform which, at this point, must be easily manageable by Zabbix.

Thanks in advance for your advices.