The M.2 SSD you have now has specs that indicate 1680/860 read/write speeds, nothing really outstanding as far as M.2 NVMe SSD are concerned. You can install up to and including a 4TB NVMe M.2 SSD as the Crucial page for your system indicates here. The specs on the Crucial you listed are for a Gen 4 SSD and your system supports Gen 3. Even at that the read/write speed would be around 3600/3000, much better than the SSD you now have. As far as other SSD options are concerned, this Amazon page has a number of alternatives keeping in mind these are Canadian prices but Amazon USA would have similar models.
TLDR to the questions towards the bottom. So, I am wanting to upgrade my C: drive.  The sk hynix bc501a 128gb 2230 m.2 NVMe isn't cutting it.  My G5 did come with a 1tb Seagate barracuda  sata drive.  Most of my stuff currently goes to the sata.  Userbenchmark shows "Max speed: PCIe 5,000 MB/s---SusWrite [NAME] intervals: 104 86 75 64 66 60 MB/s" , which from what I can determine, the system itself can do up to 5000 mb/s, but the tests were muuuuuuch lower than that on the write speed, did not give a read speed.  CrystalDiskMark  ran as follows: [Read]SEQ 1MiB (Q= 8, T= 1): 1562.577 MB/s [ 1490.2 IOPS] < 5298.00 us>SEQ 128KiB (Q= 32, T= 1): 1564.896 MB/s [ 11939.2 IOPS] < 2595.21 us>RND 4KiB (Q= 32, T=16): 276.153 MB/s [ 67420.2 IOPS] < 7547.39 us>RND 4KiB (Q= 1, T= 1): 36.894 MB/s [ 9007.3 IOPS] < 110.80 us> [Write]SEQ 1MiB (Q= 8, T= 1): 179.224 MB/s [ 170.9 IOPS] < 46327.69 us>SEQ 128KiB (Q= 32, T= 1): 176.191 MB/s [ 1344.2 IOPS] < 23737.16 us>RND 4KiB (Q= 32, T=16): 182.185 MB/s [ 44478.8 IOPS] < 11487.74 us>RND 4KiB (Q= 1, T= 1): 99.214 MB/s [ 24222.2 IOPS] < 41.10 us>. That still comes back as a far cry from some of the speeds I would expect.   Intel Optane Memory and Storage management states "There is no valid disk pairs in your system", which I am guessing means since I have a NVMe, that it is a moot point.  If I am not mistaken, that is just to boost perfomance of the SATA. I have looked and digged and cannot find what the specs are supposed to be on the nvme for read and write speeds.  The recommended upgrade from Dell Dell M.2 PCIe NVME Gen 3x4 Class 40 2280 Solid State Drive - 1TB | Dell USA does not list the speeds either.  Crucial memory recommends up to 4tb nvme drives, and 6600 MB/s Read, 5000 MB/s Write.  BUT, the manual for the G5 states "M.2 2230/2280 solid-state drive PCIe Gen3 x4 NVMe, up to 32 Gbps Up to 2 TB"  TLDR What is the real specs of the currently installed NVMe: Is the system actually limited to a 2tb nvme, and what other specs? Is Crucial P5 Plus 2TB PCIe M.2 2280SS Gaming SSD | CT2000P5PSSD8 | Crucial.com a good buy, since it is twice the storage at almost half the price of (the un specificationed) Dell M.2 PCIe NVME Gen 3x4 Class 40 2280 Solid State Drive - 1TB | Dell USA ?   Or does anyone know of one even better at a below $180 price? Thank you for any all help in this matter!    
Dell G5 5000 nvme upgrade and specs info for soon to occur upgrade