Let's Talk about Privacy and Security

Yesterday, I switched to Firefox completely on desktop and Mobile both. I noticed My chrome Automatically adding “?ref=XYZ” to some links. I don’t use any extension so I decide to change my browser.
On Firefox, I’m using two addons, UBlocks and HTTPS Everywhere. For Web Designing and Development I switched to Chromium (open source version of chrome)
I’m not sure switching Browser is enough or not. I don’t use any anti-virus except window security. I haven’t updated my window since I bought my new laptop (very bad experience with window updated in past)
Please tell me, How you protect Yourself from trackers and hackers.
Which antivirus is best? or They’ll useless?

Maybe these extension help.

Thanks! Saw your Latest Plugin, very brilliant Idea to filter bot.
Do you recommend any anti-virus or anything. Because I’m 100% against window updates which means there anti virus will expire after few months.

Adware Removal Tool by TSA, Hitman Pro - these two are my favourites. I don’t always use any Anti-Virus except builtin Win 10 one. But in rare case, I prefer softwares like these.

If you suspect your system, better re-install and keep important files encrypted at Cloud.

Also, Chrome has inbuilt feature to detect harmful software.