Does font size affect file size? What is xlsb file extension?

I have a sheet for function STOCKHISTORY of thousands of symbols, it is 12 point Times New Roman font, maybe I can change it to 8 points (I don't directly view this sheet, but my VBA code bases on this sheet).

Does font size matter to file size? My current file exceeds 5MB and I am thinking to reduce the file size a little bit. Make it lighter and run smoother. But does it matter a lot, if font size has only little effect on file size, I will leave it alone.

What is xlsb extension? Does it affect any VBA macro? But it does not save anything on file size (for my file). I am using xlsm extension.

Thanks.