Hi @Dpdfuzz welcome to this free user-to-user Alienware laptop discussion forum. 

The PCIe NVME Gen 3x4 OS (C:) boot drive should be a large capacity ultrafast M.2 2280 SSD card (Dell Class 50+ performance. Best in class PCIe NVMe). Example: SSD 970 EVO Plus NVMe M.2 2280 2TB Memory & Storage - MZ-V7S2T0B/AM | Samsung US with 3,500MB/s Seq. Read. 

Alienware m15 Ryzen Edition R5 Storage, up to 2TB M.2 2280. NOTE: The performance of the PCIe NVMe Gen4 x4 will be limited to PCIe Gen3 x4 bandwidth on this system. 

Alienware m15 R5 | Memory RAM & SSD Upgrades | Crucial.com up to 4TB M.2 2280. 

The M.2 2280 SSD Thermal Shield for Dell Alienware M15 Ryzen Edition R5 is DP/N 26X1Y. Search online for discounted purchase with screws. 

Thank you very much for your reply. 

In other words are you saying  that I need both of these that linked above?  And the first one you listed will replace what I currently have as my (C:) boot drive? 

Hi @Dpdfuzz thank you for sharing more questions. 

What fast or ultrafast SSD is currently installed in the Alienware m15 Ryzen Edition R5 notebook?  

In the opening post, you asked about the difference in Dell SSD Classifications. Dell Class 35 & 40 isn’t any sort of industry standard. You should start by comparing the sequential read/write speeds (MB/s Seq. Read and MB/s Seq Write) with other SSD cards. Then look at the other features that you want to use, such as ability to encrypt SSD just in case the laptop goes missing with your bank account information. Automatic Windows Device Encryption or BitLocker on Dell Computers | Dell US   

In the opening post, there is question about replacing the current SSD or adding to storage capacity. Do you want to install a large ultrafast SSD card to improve response of the (C:) boot drive or just a large fast Data storage SSD card or both?  

Hello again thank you very much for your reply.  According to the System Info I have a BC711 NVMe SK hynix 256GB.  I purchased it for my son.   He quite often complains " Dad, I can only fit a few games on here... There's no way I'll be able to play GTAv"...      That's my dilemma and I am aware the amount of storage that game requires.   This is all im trying to do for him without breaking the bank.    I hope that helps.    

Hi @Dpdfuzz thank you for sharing update. 

The ultrafast M.2 2280 SSD PC/BC711 NVMe SK hynix storage capacity range is 256GB to 1TB.

The first slot M.2 2280 SSD (C:) boot drive should be 2TB or more. This should have plenty of empty space so that all the gaming temporary files can be quickly unpacked and used. 

The second slot M.2 2280 SSD should be used for DATA storage and have personal files, etc. that are not required to be on the (C:) boot drive. (All applications must be installed on the boot drive, not the Data drive.) 

Is the SSD 970 EVO Plus NVMe M.2 2280 2TB Memory & Storage - MZ-V7S2T0B/AM | Samsung US with 3,500MB/s Seq. Read or similar within your price range? Especially now that black Friday deals are available this week? 

Yes it is affordable at 2T.  And just to make sure I understand,. Is this going to replace slot one? 

And Slot 2 will be Alienware m15 R5 | Memory RAM & SSD Upgrades | Crucial.com up to 4TB M.2 2280. 

Apologies!   Truly! One further question. 

What would the difference be in the 

 SSD 970 EVO Plus NVMe M.2 2280 2TB Memory & Storage   

        models#

MZ-V7S1T0B/AM and MZ-V7S1T0.   I know you specified the first model #.   I'm just noticing the latter is cheaper.  

Hi @Dpdfuzz thank you for sharing request for comparison. 

It is always prudent to get a discounted purchase and look at best deals for 2022 on the internet. The Samsung 970 Evo Plus is repeatedly voted best in its class. There are other evolving contenders.

Not sure about the technical difference. It may be promotional, regional and/or vendor price difference where they are sold (Canada versus USA). 

Here is an online 1TB comparison Samsung 970 EVO Plus MZ-V7S1T0 vs Samsung 970 EVO Plus MZ-V7S1T0BW | ⿻ Full Comparison (productz.com...