Welcome to Server Builds!
So right off the bat the build you have outlined is overkill for the use case you mentioned. (NAS, Media Server and Game Server)
The typical strategy here is to use older used parts with the aim of building a value server that will get you most of the performance of new hardware for a fraction of the cost. The current price performance inflection point for intel seems to be the 8th / 9th Gen platform like the NK 6.0 build.
You should be able to get the same functionality and experience with an i3-8100 or i5-8500 and save a couple hundred dollars. That said I’m not sure what the market for used parts is like in Canada. If used or older generation gear just isn’t available at a lower price then there is not much you can do, but I would scour ebay; there are many US sellers who will ship anywhere in North America and Chinese sellers who will ship worldwide.
There are a few things I would reconsider regardless:
Premium RAM
Look for budget DDR4-3200 at a lower cost. Don’t pay more for faster or lower latency RAM, you will see no benefit for you use case.
Dell HBA
I would recommend against the Dell HBA. That is very expensive; for instance the HBA in the NK6 build is $9. The branded HBAs made for Dell, HP, IBM etc may have proprietary firmware that may cause issues flashing to IT mode or may not play well with Unraid. If you need an HBA I would stick with a standard LSI or Adaptec, but I think you may not need an HBA at all.
SAS vs SATA Drives
I would also recommend against the Seagate Exos SAS drives. The reason that many of the builds on these forums have SAS HBAs is because they are buying used enterprise SAS drives dirt cheap. Used enterprise gear is really cheap but new enterprise gear is really expensive. If you are buying new you can save some money by buying SATA drives and using the onboard SATA on your motherboard. The cheapest SATA drives are the “shuckables” that are sold in USB enclosures however you never know what you are going to get and it won’t have a warranty.
Drive Capacity
The way the main Unraid disk array works is not RAID (hence Un-Raid). You give up 1 drive to parity protect all the other drives in the array no matter how many of them there are. So with only 2 drives it is similar to RAID1 in that you lose half your capacity, but the more drives you can add the smaller the proportion of your total disk space you give up to parity. So 2x 16TB drives will get you 16TB space, but 4x 8TB or 3x 12TB would get you 24TB of space. Depending on pricing you might be able to add more capacity to your array with a larger number of lower capacity drives.
Other Thoughts
I have used the Fractal Define R5 and it is a very nice case. I wouldn’t call it Sleek; it is quite large, but it is well built, easy to work in, and quiet.
In Unraid you can set up your NVME SSD as a cache pool and use it for more than just Plex data. You can use it as a cache pool for all of your docker and VM data (appdata, domains, and system) or potentially all of your shares.
Hope some of that helps.