Through several years of using web browsers, the slowness is caused by profile being too big for the storage device to access and extensions. Clear the cache and test. Turn off extensions and test. If you have done that and it is still slow, create a new profile for your web browser and test. If you use the profile from several versions ago and haven't created a new profile, the old profile can cause problems. Running multiple ad blockers is no, no. Use one ad blocker. Try disabling your anti-virus and test carefully. I have used Bitdefender and it has caused slowdowns, so I'm back to MS Security Essentials. I have found that I have no problems with MS Security Essentials.
On my setup, I install Firefox, Chrome, and Opera. I like variety. All three uses the same amount of resources. I use Opera for my daily web browser at this time. I was using Firefox. Before that Chrome. The reasons why I move from one web browser to the next is features that one web browser has out of the box without using extensions. Opera's external video window feature that I haven't seen with Chrome and Firefox. For compatibility, I always use Firefox. I use Chrome for mainly Netflix. Chrome has a lot of options, I suggest going through the options and turn off some and make a better conclusion than it uses more resources.
I suggest change your power settings to performance, but you don't have to do this. Change the time to put your hard drives in standby to never. Change the time to turn off your monitor to something like 5 hours or little more. Any monitor takes at least 60 minutes to be at its best brightness even though it uses a LED backlight. You might want to run pcdecrapifier. Before you do, image your drive. If pcdecrapifier didn't make your computer feel more responsive, then you have outgrown your computer or do a fresh install of Windows. When you have outgrown your computer, buy a new computer or better build your computer.
I have Ivy Bridge and Haswell based computers that became slow with Spectre and Meltdown patches. I run InSpectre from GRC to easily disable the patches. There are security issues disabling these patches, so understand the risks before using InSpectre.
