Driver issues...they can be impossible to undo, right into the registry and firmware.
Me? Since I KNOW that it was working fantastic. I would re-image. I hate a dirty OS. Gremlins.
Plus it's easy.

By re-image do you mean reinstall windows? If so then I can’t really do that as I have nothing to backup my data to.

I don't see this option labelled as such in either the boot manager or the UEFI. what should it show up as, and where exactly? (could you attach a photo or something to show me?)

Ok...so every Dell SSD comes with a separate partition with a complete Image of the OS partition, as it came from the factory. It only takes a few minutes.
IF you have changed the HDD then you lost that partition (unless you imaged the original Dell drive, with the factory-reset image on it.)
Otherwise it should work fine. I'm not sure where it is on an M15 R2. I assumed, like most systems, it was under F8. You could ask Tech Support, or perhaps someone here knows the procedure for an M15. The Knowledge base just comes up with people that have reset an M15...not how they did it.
It's a great procedure though, I do it once a year.

Re-image is under the F8-at-bootup menu.
If not, try F2 or F12 at bootup.
It will solve all your problems and more. Many drivers and firmwares don't always remove themselves very well. It can really affect the machine. Registry, conflicts and just general gremlins.
Plus you get a completely defragmented new drive with only the NEWEST updates. No remnants of old updates.

This is Dell's instructions to complete a factory restoration of the OS.
How to restore the Dell factory image with Dell Backup and Recovery | Dell Canada

how to restore dell laptop to factory - Bing

Thanks, just started it and I’m just waiting for it to finish.

well I just did the reset, no dice, the values are still being reported incorrectly.

When your installing the driver for NVIDIA select the latest option and do a clean install using the GEFORCE EXPERIENCE application in the driver custom installation. 
https://www.youtube.com/watch?v=DOjeE4wY-1I

This partially solved the issue, performance is much better than before, but still not at the same levels that it originally was. the values are still being misreported as well.

So, when you received your your machine, your machine was, at one point, working as spec, even overclocking, etc....in what sequence did you apply all of your updates?
Can you repeat the process...even taking an older version of Bios...etc.?

it was indeed working as it was supposed to back when I first got it. Never did any overclocking since I was already CPU bound in a lot of games I play (e.g. doom eternal as an example) and I can't OC the particular CPU I have. I did the updates in the same order I did them when I got it, windows updates first, then nvidia drivers, then whatever was left in Alienware Update (except for bios updates, which I do separately if they're available), then whatever software I was going to use. The issue occurred well before/after I did any bios updates, so I highly doubt it would solve anything.

Update = After completing troubleshooting, a DELL-Cares agent setup service.