You can mount network storage and use MX Player, but Plex is probably the easiest setup to accomplish

I think the best way to do this would be to install Plex server on the MacBook and Plex client on the Shield

Nvidia Shield TV has a Plex server on it. Just plug in your external drive and then configure Plex to use it.

I already have plex server installed on my macbook, but was trying to get a solution where my macbook can be free. So if i buy a WD my cloud 4tb type NAS, and plug that into the router, will I be able to access the media on it through the shield, also will I be able to access the drive to write files to it?

Lastly, I tried to play a file with truehd 7.1 on my amazon fire tv, but it said that the device does not support it and thats why the audio was transcoding. So if I play the file on Nvidia shield will it be able to play truehd 7.1 audio, or do I also need to have a soundbar that is capable of playing truehd?

Archos Video Player might help you out. You can use your external drive, or network drive, and everything runs off the shield itself.

I tried plugging in my NTFS formatted external drive into the shield but it keeps saying that I need to format it. Before I do anything I want to know the right way to do it.

Also if I plug my NAS into the shield I won't be able to plug it into the router as the router is not in the same room as the shield. I want a solution where I can keep the NAS plugged into the router, but still be able to access through various media streaming devices in different rooms of the house, I also want the ability to write files/download movie files into the NAS using my macbook.

Have your NAS do what a NAS is supposed to do. Just have it connected to your network and serving files.

If you want to connect an external hard drive to your MacBook and access your files that way, you should be able to setup Plex server on your MacBook and add the external drive to the library.

Unless theirs a particular reason you need to do this through your MacBook, I'd recommend using your NAS. I do not recommend using your NAS as a Plex server doing the transcoding though. Depending on the specs, it most likely will not be as smooth as just serving the files and letting the client transcode. The Shield should be capable.

I tried plugging in my NTFS formatted external drive into the shield but it keeps saying that I need to format it.

Also, Any particular NAS that you guys would recommend to use with Shield tv?