Generally not.

If your production system is managed competently, I'm certain that there are engineers that can assess risk vs. performance and whether spectre and similar issues warrant those mitigations in your specific environment and make the appropriate design decisions.

If on the other hand your system is managed by "best-practices", distro defaults, and what "some-guy-on-the-internet said", well then you have much bigger problems.

Also, best website ever.

My gut says that single user machines it doesn't matter so much, however these same machines probably run a lot of untrusted JavaScript that may be able to exploit things.

A crud rest service receiving requests from the open internet, probably a bad idea to disable mitigations on that machine.

On the other hand, a video transcoder or similar picking tasks off a queue and writing back to storage maybe it's fine? Though I'll admit I'm not sure that there wouldn't be ways to cause (sensitive) data to get into the output file, so would default to leaving everything enabled, especially since the input to transcode would be arbitrary

2) No, most people (not just engineers) are bad at risk assessment. Like thinking "my single user system shouldn't care about this".

3) I was talking about prod environments, not your random laptop.