Is it possible to connect to remote server using vnc or rdp from within tails?

The linked guide describes how to connect from a Linux client through Tor to a VNC server running on a hidden service .

It should also work for connecting to non-onion VNC servers through Tor, and on Tails provided that you tell torsocks what SOCKS port Tails is using. It might be 9151, though I couldn't confirm if that's current.

VNC Remote Support via Tor Onion Services

For your case, the guide should boil down to 3 steps (though I have not tested):

1. Set an administrator password in Tails' startup options.
2. After startup, install torsocks and a compatible VNC viewer:

   amnesia$ sudo apt-get update && sudo apt-get install torsocks xvnc4viewer
   

   Enter the Tails admin password you set when prompted. The package manager update can take awhile. If you've set a persistent volume, it's possible to configure automatic installation on boot.
3. Run the VNC viewer through tor:

   amnesia$ torsocks --port 9151 xvnc4viewer example.org
   

   Replace 9151 with Tails' tor socks port, and example.org with your remote VNC server IP or hostname.

Note that torsocks is not generally a safe way to tor-ify programs, in the case that the program may use networking library calls that torsocks does not know to override.

However, Tails' firewall is designed to prevent any outgoing connections except through Tor, and thus should prevent any leaks. i.e., torsocks is generally safe if used within Tails.

It is listed among the design specifications but it seems that it does not come with a client by default and requests for this have already been denied.

https://tails.boum.org/contribute/design

Quick google search turns up a reddit post suggesting that it is possible but troublesome to setup due to the behavior of the firewall. https://www.reddit.com/r/tails/comments/50gyvz/tails_issues_with_rdpvncteamviewer/