Masked Camera Input as Screen

Hello everyone,

so I want to make a camera setup, where a static perspective camera is used to capture the whole scene but only a masked area of it is shown to the screen, filling it.
The cut out area should follow the player and it should be limited in X and Y coordinates (not moving further than x).
The reason for this is so you get a perspective shot of the whole scene and not only a camera following the player which changes its perspective upon moving.

Now I tried messing around with Render Targets but the problem is you’d have to give them a huge texture size which is impacting performance too much. F.e. if I want the screen to be 1080p, the render target would need to be at least 3 times as much.

I’m not well versed with post process materials and blendables yet, but I think there might be a way like this too.

Would be really glad for any suggestions, if you’d have to code it I’d be glad for a few tips.