My panorama is blurry

Hi!

I'm currently working on a 300cm x 30cm drawing. When it is finished, i will scan it and stitch it together. Then i will place it on a canvas that is 150cm x 300cm (because of the required panorama size 1:2). Now i see that i have a problem with my panorama tests. It is obviously way too big to preview or upload somewhere: It look super blurry when converted to a 360 panorama. When i copy the file and scale it to a smaller canvas, it looks also very bad and pixely. I assume that is just because of quality loss. How can i continue drawing on this big format, but be able to translate it to a smaller, usable image size later for the online 360? Do i do that while scanning? I need it to look sharp in the online 360 file.

Thank you in advance!