Connecting Apple TV HD to a 2017 Samsung TV?

Yes, you can use the Apple TV HD on any Tv with an HDMI port. You can use any HDMI cable. Since it's not 4K, you don't need a high bandwidth cable. Any normal HDMI cable should work fine.

The flash drives though are bit confusing, since you cannot plug a flash drive directly into an Apple TV.

The Samsung TV model appears to have a USB port, so you can plug flash drives into that, but then the Apple TV is not involved.

I would mainly play mp4 from USB flash drives.

You wouldn’t need an Apple TV box to play mp4 media from USB flash drives. Many semi-modern TVs have that functionality built-in.

To play your own media files through the Apple TV box, you would need to load that USB drive to a computer, and then Home Share or Plex or similar, that from the computer to the Apple TV box through the home network, which would then send that through HDMI to the TV.

You can connect the Apple TV to your network, and yes, Airplay content to it from the Mac.

If your TV supports Airplay you can do the same thing without the Apple TV.

click here ➜ Apple TV app & AirPlay 2 Enabled Devices - Apple