Use of heat mats during veg/flowering? Any undeseriable aspects?

So in the space I use, it can get a bit cool during lights out time. I really hate leaving heaters and the like unattended so I was considering how to keep the root system comfortable.

I was looking at heating solutions for a 2x4 area (really 4x4 but want 2 separate sub-areas so I could split/downsize to 2 separate 2x4's if needed) and was seeing seedling heat mats that were 2x4 in nature.
I also was seeing some of those heating 'cables' but they must be fully buried from what I read. So no go there.

I'm currently using an amended soil mix and will be trying to keep a good micro-herd healthy and going so I don't want to overheat things - so I'm not sure what my target root zone temps would be. The area is ventilating and drawing from an interior kept in the low 70's for ambient but it still gets a tad cool on the floor especially.

Any reason to not just snatch up 2 of those 2x4 mats with the temp controller just like you'd use for a shit-ton of seedlings? Target temps I should aim for?

Open to other suggestions as well. i.e. should I aim for heating the room itself since the plants - not just the rootballs - need that warmth as well... Something I'm missing?

The little tiny heaters that you can get for like 20 bucks work great for the space you're working with friend. They have a kill switch that shuts them off if they get knocked over, so I wouldn't worry about the heater doing anything fire starter wise lol. It would be cheaper and more effective at keeping your entire room environment stable and keeping your floor warmer for your roots.

My grow is in a new england basement. Temps will drop to the low 60's or even the high 50's if I don't use heat of some kind.

So what I've done is add a small ceramic cube heater to the tent connected to an external thermo controller. The one on the heater is far too imprecise or stable to use. I just use the external one to kick on at 70 and off at 73. It usually only comes on during lights out.

I also added a heat mat under each of my sip grow boxes. I noticed the soil was staying cool even though the air was warm because the concrete floor was chilly. So I put some styrofoam insulation board down and put the heat mats on that, then the sip containers.

The only negative I see is that I go through water in the res faster, but that isn't a huge deal. It does keep the humidity in the tent up, which is another plus when it's 20% in the basement. But the soil and air are warm, and the plants seem happy.

By far, the one thing that had the biggest impact was getting that pink styrofoam insulation between the floor and the bottom of the pot, even if nothing else was done,

I do like you though and put the heat mat on top of the insulation and under the container. I get the 1"x2'x2' pink insulation sheets at HD.

Even if you have no other heat source, just insulating the bottom of the container from the concrete floor is a tremendous help.

Yeah keeping your pots off the concrete alone will do wonders for keeping your root zone warmer. I grow in a basement in Michigan, where it can get down into the 40s if I don't use a little heater. But I just use one of those same little heaters and it keeps the temps stable as long as the heater kicks on when the lights go off.

Yeah I have some old foam board from prior projects stashed somewhere in an attic. Need to get up there and drag a few pieces out. Given that my ambient is fine in general and it's really just the floor contact sapping the heat away I ended up going ahead and ordered two mats. Given how much they want for the temp controller alone in many cases this seemed like a decent deal...
VIVOSUN 48"x20.75" Seedling Heat Mat and Digital Thermostat Combo Set" for $44 bucks on Amazon - mat and temp controller combo so we'll see how that works out...

foam -> mat -> smart pot... Directly placing the pots on the mats unless someone can share a reason not to do that. They say not to cover those mats or they may overheat so... I'd assume that means if you did need to have things without direct contact you'd need an air gap of some sort but that'll lose heat in itself.

Just keep a close eye on the moisture levels. Your pots will dry out faster.