Good low light is relative. mFT will have better (pre processed) low light performance than a phone. The 16MP (Pansonic) and 20MP (Sony) sensors used in those mFT cameras have very low read noise, which helps with low light as well. It still has a big sensor, bigger than your FZ1000. My experience with phone photos in low light is that they look fine on a phone screen but they don't hold up under any degree of enlargement. And in the end low light performance is a matter of lens aperture, not sensor size. An mFT camera with an f/1.2 lens will give better low light performance than a FF camera with an f/2.8 lens.
That is NOT what many others say here that have actually experimented w/ the difference, especially w/ the "stacking" ability of the newer cell-phones, (technology that both the FZ1000 & RX10-IV also have).
But at what cost ... ???
The FZ1000 is a fixed-lens camera. It has a 25–400mm (35mm-equivalent) f/2.8-4.0 zoom lens that is permanently attached to the camera. There's no point in getting a Sigma 56mm f/1.4 lens for it as there's no way to mount another lens on the camera.
The NEX-5N that I was using ten years ago had a Hand Held Twilight mode that used stacking, so it isn't new.
Since we're dealing with low light performance, which is limited by noise, we might as well put in all the equivalences if we're going to give the OP a good idea what he's dealing with.
The fact remains that the intrinsic low light ability fo mFT is one stop better than the 1" compacts and 3 stops better than most phones. Some cameras have automatic stacking if you want, but it can be done with any camera with the right software.
I can't see any useful information in that post. We aren't talking about daylight.
It has a 25-400mm-EFL f/7.6-11 EFN lens. Not what you want for low light. If he gets the mFT system he can fit the sigma 56/1.4. (112mm EFL, f/2.8 EFN) I have one, it's a very nice lens.
What Joe means by "better IQ" is that the FZ1000-II has much better image quality than the FZ300, not much better in general. The main reason the IQ of the FZ1000-II is better than that of the FZ300 is the difference in sensor size. By that measure, a so-called "Full Frame camera", like a Canon EOS R6 has an even greater IQ advantage over the FZ1000-II. But you aren't going to find a new full frame camera in your budget (or even a new FZ1000-II).
What would be a good MFT model for the OP to look for used ?
Several Oly bodies have a multi-shot capability.
Perhaps because of the $500 budget limit, but not because of the -4Ev capability. Many MFT bodies can do this.
I tested iPhone 13 Max Pro and m43 in low light. After processing m43 with DeepPrime and adjusting inLrC, the m43 image looks much better on a computer screen. The iPhone image has smudgy, ugly shadow details.
Specifically for low-lighr ???
Well, the original FZ1000 (-4EV) was under $500 until the "II" and raised it back to $800 ....
As I said, he can get a new GX80/GX85 or G7 with kit lens in his budget. For used there's loads of options, he could look at the E-M10 or E-M5 line. Looking up on Ebay US site, there are plenty of E-M5 Mk IIs at less that $300, which leaves budget for a much better (faster) than kit lens. Mk III's go above the budget. On the Panasonic side There are GX8 bodies less that $350 and some G8 bodies less than $400.
There ya go confusing beginners again ... for exposure/lightness considerations, it is f/2.8-4.
In low-light, you are just fighting to "get-thw-shot" (exposure/lightness).
Of course it is not (a universal solution to all problens), but neither is FF/APS w/ (single FL) prime lens, (since most zooms start @ f/3.5-4).
I'm not sure if I agree with bobn2's statement here, either.
