How to make geometry retain its size regardless of the size of the renderer - Plane changes size depending on screen size

Im having an issue where the plane I made seems to change size based on size of renderer. I just want the plane to maintain the same pixel size reguardless of render size. Ergo, if I make it 300px wide it should stay 300px wide reguardless of render size. Ive made a stackoverflow question with the issue which contains a deeper explanation, a codepen, a gif and directions to the code I suspect of being relevant



Issue now solved thanks to Darkmatter on the three.js discord. Solution is now in the stackoverflow