Question

For continuous task, for example rendering an animation, would creating short lived threads every frame be a lot slower than creating threads at the start and then pausing them and resuming?

Or will the difference be negligible?

Answer 1

That would be a lot slower; threads have a large overhead.

You can use a threadpool to re-use threads and avoid the overhead.
However, it is probably still not worth using threads for such short-lived tasks because the costs of context switches will outweigh the benefits.

Measure it!