In fact my browsing is faster (on known sites) with those extensions and my custom user.js than without.
But it was hard work to get to this point, since i block everything except CSS & pictures until i whitelist it.
So i have to figure out what to whitelist to unbreak things etc.
After that point, there are no ressources loaded i don't want, which speeds up the general surfing until i hit a new site which i haven't whitelisted.
But this is a trade-off i can gladly accept.
To the Bitdefender and Malwarebytes thematic, i already said that i never experienced any problems with while both have real-time protection enabled.