Best software is subjective, but HWInfo is generally considered one of the best options. It provides very detailed sensor readings, including per sensor NVMe temperatures, and is more accurate than HWMonitor.
Regarding your temps, 66–70 C under heavy load is not ideal, but still within safe limits. If your other components run cool the NVMe is likely sitting in the slot right under your GPU where airflow is poor.

Do you have a second M2 slot with better airflow? Moving the drive can sometimes make a huge difference. If not adding an M.2 heatsink is a good idea. A decent budget heatsink for around 10 bucks usually drops temps by about 5–10 C, which helps extend the SSDs lifespan and reduces the risk of thermal throttling.

For your Kingston NV3, thermal throttling typically starts somewhere between 70 C and 85 C, depending on the controller and firmware. Even if throttling kicks in, most gaming scenarios wont show a noticeable impact because modern NVMe drives are so fast. The only cases where it might matter are during large installs, game updates, or streaming-heavy open-world games, where it could slightly affect texture loading.

edit:
Avoid the very cheap heatsinks with rubber bands and go for one with a proper metal clip or screws for good contact.

I'm kind of decided with a heat sink + 3 cases fans. Just not sure if I should get a fan hub. 4 fans on the single board connector is a bit much maybe (well, just simples fans, no lights).

A fan hub wont help with your NVMe temps and it’s only useful if you need extra headers for multiple fans. Adding more case fans probably won’t change much either, since your overall system temps are already low, which means your airflow is fine. Doesn't rly make sense tbh.

The real issue is likely the NVMe placement. If it’s sitting right under the GPU, it’s getting baked by the GPU’s heat and has almost no airflow.

Eiither move the drive to a different M2 slot if your board has one with better airflow or add a proper M.2 heatsink (with metal clips or screws, not just rubber bands). That usually drops temps by 5–10 C, which is enough to keep it away from throttling and improve longevity.

The extra fans are only worth it if you already have poor airflow or hot CPU/GPU temps, which doesn’t seem to be the case.

Originally posted by Schrute_Farms_B&B:

A fan hub wont help with your NVMe temps and it’s only useful if you need extra headers for multiple fans. Adding more case fans probably won’t change much either, since your overall system temps are already low, which means your airflow is fine. Doesn't rly make sense tbh.

The real issue is likely the NVMe placement. If it’s sitting right under the GPU, it’s getting baked by the GPU’s heat and has almost no airflow.

Eiither move the drive to a different M2 slot if your board has one with better airflow or add a proper M.2 heatsink (with metal clips or screws, not just rubber bands). That usually drops temps by 5–10 C, which is enough to keep it away from throttling and improve longevity.

The extra fans are only worth it if you already have poor airflow or hot CPU/GPU temps, which doesn’t seem to be the case.

Only 1 slot, so no moving the m.2. A heatsink and some more fans might help. My guess is that the m.2 is not getting much airflow as the path is kind of blocked by the GPU and CPU/cooler. And I only have 1 case fan.

Something is not right.
After a good night's sleep I turned the computer on and I get the temps for the m.2:

Assembley: 35ºc
Sensor 1: 55ºc

Took 15/20 seconds to boot and turn on HWMonitor. It's 23ºc in the room.

This overkill (it's cheap though and good reviews)?

https://www.amazon.es/gp/product/B0BNHYM6Z4/ref=ewc_pr_img_1?smid=A1K0HRPQTHRQOO&th=1

Honestly, I am not totally sold on the design. Yes, it's big and looks like it can "carry" heat quite well but the "fins" and grooves are sideways (as in most similar models) while the airflow is usually lengthwise (at least in most cases I've seen... and pun intended) as in front to back. Would make more sense to me to allow the airflow to go between the grooves on the fins so to better remove the heat and increase efficiency. Might just be me.

Something more like this maybe:

https://www.amazon.es/Thermalright-Enfriamiento-disipador-Enfriador-computadora/dp/B0BNZTMBB4

Your temps look normal for idle and just show the NVMe isn’t getting much airflow. 35 C on the PCB is fine, 55 C on the controller is still safe, these drives can handle 70–80 C. The quick jump after boot is normal since NVMe does a lot of work loading the OS and caching, and with no airflow, heat lingers.

A small heatsink will make the biggest difference, even without extra fans. If you only have one case fan, try repositioning it for better GPU/motherboard airflow. The HR-09 is good but might not fit if the GPU is right above. The TR-M.2 is safer, but I prefer Arctic heatsinks, they’re simple, include proper pads (and they are easy&safe to remove which is a huge plus in my book), and gave me ~10 °C better temps back when my 7900XTX was cooking my NVMe. Now with a 5090 and good airflow, my drive stays around 40–50 °C under load.

And you’re right about fin orientation, it doesn’t really matter unless you have a fan blowing directly on it. For tight spaces, low-profile beats tall and fancy every time. Looks sharp though.

Originally posted by Schrute_Farms_B&B:

Your temps look normal for idle and just show the NVMe isn’t getting much airflow. 35 C on the PCB is fine, 55 C on the controller is still safe, these drives can handle 70–80 C. The quick jump after boot is normal since NVMe does a lot of work loading the OS and caching, and with no airflow, heat lingers.

A small heatsink will make the biggest difference, even without extra fans. If you only have one case fan, try repositioning it for better GPU/motherboard airflow. The HR-09 is good but might not fit if the GPU is right above. The TR-M.2 is safer, but I prefer Arctic heatsinks, they’re simple, include proper pads (and they are easy&safe to remove which is a huge plus in my book), and gave me ~10 °C better temps back when my 7900XTX was cooking my NVMe. Now with a 5090 and good airflow, my drive stays around 40–50 °C under load.

And you’re right about fin orientation, it doesn’t really matter unless you have a fan blowing directly on it. For tight spaces, low-profile beats tall and fancy every time. Looks sharp though.

Thanks,

I actualy like artic but I can't seem to find it over here. I guess it will be down to availability.