Just set mitigations=off if you want this, it's a meta-parameter that enables all the others. I used to run it on old hardware (Haswell) because of significant impact of all those mitigations on IO performance. It's not a problem anymore on my newer Zen 4.

Probably a bad idea in the general case if you work with anything remotely private (ssh keys, banking) and browse the internet routinely. I visit few weird sites and block JS almost everywhere, so it both made sense to me and was relatively safe.