Find a remote part of your house where all the noise won’t interfere, it also can increase your power bill if left on all the time, you can lower the power consumption via UEFI settings at the cost of performance. Usually you can power up and down dell servers from idrac, it’s another ethernet cable you have to add to your networking, sometimes the servers have a license on the idrac that allows you to install everything via network, sometimes you don’t even need a usb and can use virtual media. If idrac doesn’t work, try Wake on LAN, it’s a special packet you have to send to its mac address via the network and it will power up the server when needed. Learn about RAID levels and decide what to do with those disks, decide if you want to prioritize space or performance. Get a usb drive and install Ventoy on it, it will make it way easier to try different linux distros, or windows, you just copy the ISO files instead of formatting the usb every time. Virtualization stuff like proxmox would be a great start if you want to learn that, specially if you find something that requires multiple OS, or you can just install a normal distro and go the container route. Things that are way faster to do on your server vs your NAS would be transcoding to reduce storage consumption of media files.
Depending on the license it has it should let you power on and off the server, see the screen (even if there is no monitor attached) and control it and could let you remotely attach ISOs to install an OS. You can get away with a small cheap gigabit switch to plug both the server and ipmi/idrac and also the network cable to your router, keep in mind adding a lot of those to the network may degrade it, but a single switch won’t harm much. The correct business practice should be separate vlans on a fancier switch and lacp uplinks, absolutely overkill for home use.