Watching device will help more with secondary AWPing or even passive primary AWPing.
Allu and GuardiaN also good examples.
GtR,Happy outdated players but great lurks to learn from.
Niko will be a great player to watch if you have good aim. His crosshair placement, positioning,etc.
Dupreeh,apEX(2017),hobbit,etc for entries.
For support, learn the flashes and try as much to not get killed while throwing nades. Also try to never get lined up with your entry fragger, many supports commit this mistake.
Don't be too aggressive until you have that role or you're highly skilled.