Do you think it is safe and secure to disable Mitigation in Fedora for the sake of performance?
I've seen a video from CTT demonstrating the <10 performance boosts by simply off the mitigation. The system will be secure for personal use as before.
It depends on how importent security is for that system and how devestating it would be if someone else got control over it and all accounts and devices connected to it.
Assuming there are sucessful exploits it would be like running everything as root and disabling all sandbox/isolation features from the kernel and browsers. I'd say you should not connect such a machine to the internet.