xpenology.org - Synology DSM on Your Own Hardware. This way, you can set up your own DHCP and manage the system just as if it were a Synology. I have not done this, but I like the Synology DSM OS. However, I do have experience with Windows Server, and it's not as secure as you might think, unless you know all the steps to take. Otherwise, you might encounter security problems. You might also wish to get your own router and have Spectrum provide just a bridged network connection.
If you would like to get fancy, Asus has its own VPN and DHCP services, and most of their higher-end routers include built-in NAS services. I also recommend Pi-hole, so you can manage all DNS requests and create your own local domains, like movies.local and music.local. This allows you to set up the VPN, and all your family and friends can just type in domains for device addresses.
If it were up to me, I would not use their equipment and would instead use and configure my own router.