In your case putting the NAS in a separate VLAN is almost certainly a bad idea.
Traffic on the same VLAN/subnet does not go through the router.
However, unless you are using layer three switch(es) any traffic between VLANs must go through the router.
Have you already purchased the NAS?
Qnap NASs have official support for multiple tagged VLANs. With Synology there is only unofficial support such as:
If the NAS doesn’t support VLANS, it probably makes more sense to put the NAS on the same VLAN as the desktop PC.
If the Android box or TV needs access to the NAS then you would have to create firewall rules to allow access through the router.
Do you have a printer on the network? If users on more than one VLAN need access to the printer you would also need
additional firewall rules. Alternately, you can setup this as a print server with multiple VLAN support:
Using multiple subnets can get complicated.
Traffic on the same VLAN/subnet does not go through the router.
However, unless you are using layer three switch(es) any traffic between VLANs must go through the router.
Have you already purchased the NAS?
Qnap NASs have official support for multiple tagged VLANs. With Synology there is only unofficial support such as:
Secure Home Network: How to Connect Synology NAS to Multiple VLANs
In a previous post, I discussed my setup of a Synology NAS. I have multiple VLANs at home, and I find a need to connect my Synology NAS to some of them. My NAS device has two network interfaces and can be connected to different VLANs on each interface. However,...
baihuqian.github.io
If the NAS doesn’t support VLANS, it probably makes more sense to put the NAS on the same VLAN as the desktop PC.
If the Android box or TV needs access to the NAS then you would have to create firewall rules to allow access through the router.
Do you have a printer on the network? If users on more than one VLAN need access to the printer you would also need
additional firewall rules. Alternately, you can setup this as a print server with multiple VLAN support:
Using multiple subnets can get complicated.