Help needed to understand NVME/SATA ssd types.

Right my system is an Acer pre-built, it comes with a 1Tb SATA HDD and a 16Gb Intel Optane cache. The system works perfectly, I have no issues really but I was considering swapping the Optane module out for a normal NVME SSD.
To me it makes sense because instead of relying on the Optane system to cache most used programs a 500Gb NVME system drive (or maybe a 1Tb if I can stretch to it) would accelerate everything, all the time, allowing me to use the HDD just for personal files, backups etc.
A small caveat is that Optane seems to interfere with Macriums disk imaging (so another reason to change).
However I have just spent a good 2 hours scouring Amazon for suitable NVME drives and I'm completely confused.
At first I looked on Intel's site to determine the connection for the Optane, it is apparently an m.2 2280 NVME PCIE 3 device, in the image it has 3 edge connectors (1 is a "B" key, 1 is a "M" key, and the middle 16pin?, I assume the data connectors).
So I tried to find the same in a NVME drive, all I could find at first were for example EVO drives stating NVME PCIE 3, but with only 2 edge connectors, then I found NVME PCIE 3 drives with 3 edge connectors, then SATA 3 SSD's with 3 edge connectors.
So my issue is, if my motherboard socket is an m.2 (mechanical key "B") as reported by HWInfo does it matter how many connectors are on the replacement drive, are 3 connectors for wider compatibility? Or do I need a drive with 3 connectors to make it work?
And why are some of these drives listed as SATA 3 and others as NVME and others as PCIE3?
Anyone who can shed some light (preferably in non techno-bable) please?

You have basically 4 types of SSDs interface.
PCIe - The SSD card is connected to the computer by a PCIe slot

SATA - The SSD is connected to the computer by a power connector and a SATA cable

mSATA - The SSD card is connected to the computer on a mSATA slot

M.2 - The SSD card is connected to the computer on a M.2 slot


SATA - It has 2 sizes
2.5" - It's the size of a laptop HDD
3.5"- It's the size of a desktop HDD

SATA - It has 3 speed interfaces
SATA 1 - 150MB/s
SATA 2 - 300MB/s
SATA 3 - 600MB/s

M.2 card - It has different lengths:
2242 - 22 mm wide x 42 mm in length
2260 - 22 mm wide x 60 mm in length
2280 - 22 mm wide x 80 mm in length
22110 - 22 mm wide x 110 mm in length

NVM Express (NVMe) or Non-Volatile Memory Host Controller Interface Specification (NVMHCIS) is an open logical device interface specification for accessing non-volatile storage media attached via a PCI Express (PCIe) bus.

This are the three options I would consider. You have to find out if the computer can boot from the M.2 drive.

1) Replace the M.2 Optane with a 128G or 256 G M.2. Use the SSD for Windows and programs and the HDD for data. Use Kari tutorial to move the C:\Users to D:\Users (HDD). You will have the speed of a SSD with the space of a HDD at low cost.

2) Replace the M.2 Optane with a 512G or 1T M.2. Remove the HDD and use it on a USB caddy for backups.

3) Replace the HDD with a 512G or 1T 2.5" SATA drive. Keep the M.2 Optane.

Lance1, I have already looked at the Crucial upgrade link, it wrongly identifies my chipset as Z370....it is actually B360, so I cant rely on its advice to provide suitable upgrades (not saying they wont work, just cant say 100% they will) as there is a lot of difference between the two chipset's (and more so since its an Acer proprietary motherboard).
Megahertz, thankyou for your visual explanation, however I think you slightly missed the point, my confusion isn't with the different standards, it arises due to the fact that I can find several makes of SSD's that connect via the m.2 port but they all have different edge connectors but also have the same designator.
Example Samsung Evo 960 is NVME but only has 2 edge connectors, Crucial MX300 is NVME but has 3 edge connectors then there are others having 3 edge connectors stating they are SATA 3 not NVME (these also have half the read/write speed of NVME drives).
As for my system, the boot priority is Windows boot manager as first device, I assume this allows to boot from NVME drives as there is no specific choice for HDD or specific ports. Other options include Optical drive, removable and LAN. I'm assuming Windows Boot manager could in theory be on any device type and that is what the bios looks for rather than specifically for a HDD.
Based on the image you provided it would seem the Corsair MP series (or similar from other manufacturers) would be the correct choice based on the connectors. The Optane module fitted currently is also a 3 connector part and reports as a NVME device.

Yeah, after digging around and looking with my trusty torch (LED head lamp, very useful) I can see that slot m.2_1 has a wireless/ blue tooth adaptor in it, slot m.2_2 has the Optane module in it. Cross checking with HWInfo confirms that.
I am currently scouring the Acer forums for info on whether my model can boot from the m.2_2 slot with a compatible device.
Im pretty confident it will boot as the BIOS see's the Optane + HDD as a raid setup, so does Windows and HWInfo, also if I disable the Optane the PC takes forever to boot into Windows so some boot files must be moved onto the Optane module when active and accessed at boot time.