Disagree here. Thinkpad P52 (16GB Ram and i7-8750H) running Windows 10 Pro. Absolutely no issues with Firefox. I always find it strange when people talk about FF issues. I never had any on Linux, MacOS or Windows. Always worked for me. Rarely do I run Chrome. I do use Edge a lot though as all my 'work' stuff resides there - Mail, Slack. It works pretty well.
I run Steam on the same machine (AoE III) with Firefox, LibreOffice Calc open as well and it's just smooth. No overheating or anything.