So, my problem is that whenever I start a machine like the "Millstone," "steam engine," or "mechanical drill," every time the machine operates, I experience a lag spike, and the more there are, the worse it gets.

I know that my PC might not be the best, but experiencing that much lag is not normal, especially for such small-scale factory.

Rubidium and Create are not working well together right now for me as well, I've had no luck in diagnosing and no logs are helpful. It's a rough one. Only thing I found of note was hiding your hud improves FPS a bit, but it's not much.

I get about 10-20fps with Rubidium on a 7700x and 7900xtx system.

Not sure how much this comment helps, but there ya go.

Things to try out:

1. Allocate less RAM to Minecraft. You have 16 gigs allocated, out of which not many is used. Please try 3-4.
2. Change flywheel backend with /flywheel backend batching and /flywheel backend off. You can switch to default with /flywheel backend instancing.
3. Does this happen without other mods, just with Create? In particular, does this happen without Rubidium?

the first screenshot is with the command and the second is without Rubidium, Initially, "Rubidium" was already installed, but there's what it looks like without it.

It's a mod pack with a few mods, there are about 120 mods, but most of them are just small additions. There are normally about 6 or 7 more important mods, like Create.

Sorry, I had a typo in previous message. I also meant /flywheel backend off as well. Though that might not improve anything, but worth a try.
Other than that I'm out of suggestions

same here, rubidioum or embeddium both lags as hell with create machines