The transcoding isn't just about bandwidth, it's about compatibility. I store most media in H.265 because that's the most space efficient, and most things can play it, but a decent number of devices still need H.264. I also have older content with DTS soundtracks, which isn't supported by a bunch of new devices.

Plex/Emby/Jellyfin will handle that compatibility by converting on the fly.

Plus, when using a Fire Stick, or Google TV Streamer, or old Chromecast it just isn't easy/possible to browse a SMB share.

Yeah I would definitely need to look into some kind of real time transcoding setup (jellyfin, etc) if I had a use case for remote watching of things on any other less-capable platforms, particularly that can't handle x265 or AV1 encoded things.

Right now if I'm not at home, and I'm watching something remotely that's served from a home fileserver, the only two client devices that I have in use are either my MacOS laptop (VLC), or a fairly recent Android phone with a file explorer app that supports sshfs mounts to open files (again VLC as the video player).