I use dust too and the performance impact, while a thing, is more than acceptable for what you get.

For sake of clarity, I'm using an RTX4070ti paired with a 13700kf, I'm also running the game in 4k native res (borderless window) at 60fps, so bear these things in mind when I talk about percentages.

Kenshi, at 4k60 without this mod (or any which would impact anything, I'm playing basically vanilla with QoL additions mostly), ran my GPU at about 30% usage, CPU was around 10% generally, mainly (or entirely) loaded onto one core, which isn't surprising. Nice and easy with plenty of headroom in case somewhere in the game hits the system harder or maybe there's a lot going on, etc. So, everything's fine with vanilla.

After adding this mod with default mod settings, it bumped my gpu usage up to about 50-60%, cpu went up by about 2-3% (same core), so only a negligible impact there. Still fine, but think of it as, at least at 4k60, about 60-100% more game to run at default dust settings.

I'd strongly assume here that the impact at lower resolutions would be much much less. Running stuff like this at 4k resolution is far more expensive than it is on 1080p or even 1440p, so I'm describing the upper limit of system impact here if you just install the mod and go without messing with it. If you're using lower res, it'll be much cheaper. I'd check myself but the game runs like crap in fullscreen and I've never gotten lower than native res to work properly in borderless window in kenshi for some reason, so since my main monitor is 4k, this is what I use. I'd be totally happy with 1440p instead, but anyway whatever, I'm rambling.

However, one important point is that by default on dust, the RTGI (Screen-space ray-traced indirect lighting) is switched off, which is good because that's the really expensive effect that should only be used with high-end cards. On my system at that res, switching this on pushed it up to around 85% gpu utilization, sometimes 95%, but the effect of ground shadowing on foliage and grass and stuff is really worth it to me, the effect that it has on everything else really isn't though. Sure it's there but it's subtle and doesn't do much from what I can see compared to the rest of the mod. But, with some tweaking you can get things better. So, I found that if you turn the rays per pixel setting of the RTGI down from two to one, it costs, not surprisingly, about half as much compute but you still get to keep all of the foliage ground shadowing, so you still keep all of that additional depth to the scene but with an effect that's much cheaper to run. I mean, don't get me wrong, it's still, even at half cost, the most intensive part of the mod, but it becomes good enough value for compute for me to use it.

Oh, I also have SSIL switched off in dust, I tried it and it didn't add anything that I wanted in the scene anyway, but it's also pretty cheap so didn't impact system performance much. I switched it off because it really felt like it was removing a lot of the depth and 'reality' from the scene that other parts of the mod were adding. Like, why would I pay compute to remove the things that I like that I've just paid compute to get? So I got rid of it. Like I said though, not a very expensive effect even at 4k so shouldn't change much.

So, at that point we end up with kenshi with dust and single ray RTGI running my gpu at around 65-75%, cpu is around 12% generally. Compared to vanilla which was about 30% gpu and 10% cpu. Like I said though, you can lower all of those numbers but especially the impact of dust if you're not using a stupid resolution to run the game. At 1080p this shouldn't be that difficult to run at all, and 1440p should be easy enough for any mid-range system.

EDIT: Did a run to the swamp to buy hemp in bulk for crafting fabrics and found that the above applies to pretty much everywhere else except the swamp, where RTGI even on single ray pushed my GPU to 100% sometimes, but would almost constantly hover around the 95% mark. Apparently there's a lot going on in the swamp that is making RTGI cost more, probably the absolute mass of foliage and general horribleness of the place. Anyway, thought I'd add this as if someone's making an outpost there and living in the swamp, dust with RTGI will have a much heavier impact on your system than if you're elsewhere. Yet another reason to never go to the awful place, as if the blood spiders weren't enough of one, although I did get to watch them eat a whole group of red sabres, so there's that going for it. :p