You really don't want to do that. watch is designed to be, um, watched. Its output is formatted in such a way as to make redirecting it impractical. While you can actually do it using something like tee, the output will be many blank lines and very little useful information.
So, in the specific case of watch, you're better off writing your own little script that does the same thing:
#!/bin/bash
This is an infinite loop, the script will run until you kill it
while :; do
Run the command whose output you want to monitor
amdconfig --odgc" "amdconfig --odgt
Wait for 2 seconds. This mimics what the watch command does
and also avoids spamming your cpu.
sleep 2
done
Save that script as ~/bin/amdwatch or whatever you like, make it executable (chmod +x ~/bin/amdwatch) and then redirect its output to a file:
~/bin/amdwatch > amdwatch.log
That will run the script until you stop it manually and execute the amdwatch command every two seconds, saving its output to amdwatch.log.
For most scripts, what you are looking for is script.sh > outputFile.txt or script.sh >> outputFile.txt. See How do I save terminal output to a file?.