Does your new computer have the same specs as the one you used before? If you still have 4GB RAM, then that's fine for work, but 8GB is what you need as a minimum for games. Is it HDD or SSD?
I wouldn't recommend running any more than 2 anti-virus programs at the same time - they will drastically slow down you PC.
There is a new mode for viewing games. If you add &Mode=UJS at the end of a multiplayer game URL. For me, this mode is faster than Unity WebGL. Note that UJS is experimental and was quite buggy when I last tried it (about 3 days ago).
Here's how to install RAM if you wanted to know how to upgrade it: https://danchurchblog.wordpress.com/2017/04/05/install-an-extra-ram-module/