Hi, there is a scaling section of the new print experience overlay -- are these controls not working properly? Make sure to choose your printer first, because Firefox stores scaling and margin settings for each individual printer.

Firefox 85-86 has a preference to switch back to the classic print experience if necessary. Here's how you use it:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

(2) In the search box in the page, type or paste tab_mo and pause while the list is filtered

(3) Double-click the print.tab_modal.enabled preference to switch the value from true (new experience) to false (classic). That should look like this after the change:

You can switch back and forth any time.

When you say "will either print gigantic or microscopic", can you clarify if the sizing issue is with the print preview (what you see on your screen) or only with the print output (what comes out of your printer)? Either way, this sounds concerning.