I have some display issues even though resolution is set normally(according to the display) not more not less. Even though I am seeing my display very big. My lock screen is fine, it has the correct resolution, but when I enter inside, the display blows up. However, when I try to power off, I can see the correct resolution in the background. I attached a picture of it
If I understand you correctly, you get very large icons when you log in, but the icon size seems to be OK on the lock screen?
You may have to tweak the Scale parameter in Settings > Devices > Displays. You can get there by pressing the Super Key (Windows Key) and typing 'displays'. In that menu, try changing the Scale parameter, and see if it fixes you icon size.
You may also try to change the Scale parameter in Fonts menu (Super key + type 'fonts' or go to Tweaks > Fonts and try changing Scaling factor or font size there. (You may need Gnome-Tweaks installed for this).