NFS for Unix-to-Unix file sharing. Security for v3 is by static IP controls and UID-mapping only. So be certain you have the IPs locked down on your network. NFSv4 uses Kerberos and is considered secure for internet use when encryption is also used. I’ve not used encrypted v4 NFS, since a full VPN is standard anyways here. NFS uses native Unix permissions, which can be very, very, handy.
CIFS for Unix-to-Windows file sharing (LAN only); Windows can be client or server. CIFS permissions are set at mount time. For something like media, permissions don’t usually get that complex until you have kids. Then it might be nice to lock down PG-13, R, and adult titles. DLNA has ZERO permissions management, BTW.
sftp/scp for any-to-Unix file management from anywhere in the world. It uses the ssh port and ssh authentication. Outside your LAN, don’t passwords, always use either ssh-keys or ssh-certs.
For streaming video, always best to avoid wifi, even if you have to buy a powerline kit. Wifi bandwidth jumps all over the place which streaming doesn’t really love. Under the best conditions wifi might get you 30-40% of the advertised speeds, in the same room, with only 1-2 devices connected and zero interference. With powerline, be certain to setup the device-to-device encryption (there’s a button), otherwise compatible systems in the neighborhood can access your LAN.
Avoid any wifi-clients that aren’t at least 802.11n at this point. A,B,G clients use too much talk-time on the RF channels and slow down everyone else. Sorta like a NYC fast-talker trying to communicate with a Texan with a slow-drawl. Attended a wifi-standards talk at a conference over the weekend.