AFAIK most reasonably recent systems such as those that would allow a PCIe connection, and run an OS such as Windows 10 do not have a "Boot Drive"
They have (as can be seen using the Storage ~ Disk Management links from the "This PC" icon
PARTITIONS labelled "System" "Boot"
The OS being run is only associated with the "Boot" facility by the OS selection list and startup modules.
That being why you can have GRUB and WIN-10 partitions on the same drive in a system.
So – where the Boot is, and it's size is only relevant in the short period until the OS startup process actually starts running.
Regarding the terminology
There is no such thing as a C: drive
Almost all storage facilities – hard drive or memory stick or SSD are IDE devices –
As in the drive comes with "Integrated Drive Electronics"
So PATA and SATA and PCI-E devices are all IDE
Additionally, there is NO requirement for the windows OS to actually run from a PARTITION labelled C:
When the startup process runs it can allocate any letter from Z down to C to any PARTITION including the one that the selected OS is running from.
You purport to have some 'Technical' expertise, so please show it by using the appropriate technology.
That dealt with – regarding actual devices in a system
Windows 10 will run on a 32GB partition –
You will of course have problems running any modern apps, or even Windows Update with just 32GB
I believe you should, for the current windows 10 management and change it for you Microsoft policy, need to have at least 64GB for the OS itself
With, maybe an additional 30+GB needed when you get to the bi-yearly update process.
So – anyone buying a system will need a 120GB level PARTITION for the OS
Regarding "Boot" – well maybe 200MB
Now, if you want to run applications or games in a fast response mode – then separate their storage from the OS Pagefile
As in a separate interface path to the motherboard
That should allow loading of programs from the drive concurrently with the OS using the Pagefile.
OK better to have enough RAM to allow you to not to have any Pagefile.
Re OS partition separate from the apps and data –
Yes – definitely not only for backup and restore purposes but also for throughput speed
allow OS processes to run on 1 device with the app (especially games) running from a separate device
Consider file processing –
OS gets asked for a file – is in in RAM cache? Is it in Pagefile cache?
Where on the device is it – scan MFT – repeat for the MFT pages – in RAM, on Pagefile)
Allocate RAM for the data block if not already done – as in page out somethings to get re-assignable RAM
Know where the file is on storage – Logical Block Nº request blocks from the device –
Is that block in cache on the device – if not load it into cache – and pass it back to the OS.
Yes - Real RAM can so much improve performance as can (if you have one) Pagefile on a fact response device.
So –
Do you need a fast BOOT PARTITION – Nope – BOOT is only done before system startup
Should you have your OS running from a fast partition – Yes it handles the I/O
Should you have your Pagefile on a fast partition – Yes if you cannot avoid one - it delays almost all throughput
Should you have the app and data separate from the OS and Pagefile – Yes especially if the device has a large cache – as in the up to 32GB optane
I would (am) looking at a system for good response under Windows 10 as
RAM 16GB at least – preferably for VM – as in sandbox and VM browsing may need 16GB for a session
CPU – at least 4 cores – see the current apps from MS
OS partition – SSD is nice – but if 32GB of Optane is available – then won't that hold almost all the files used by the OS so reducing access to the drive storage itself.
Apps partition – again Optane – another 32GB would be nice – but games etc may well have over 32GB of program and essential data – screen environment etc.
Multimedia and backup – only written once and maybe read once – and sped – well, at what multiplication rate can you watch and listen.
So – for a fast system 4+ core, 32GB RAM, 32GB optane on OS device 32GB Optane on apps device and large bulk store for installed apps and other bulk data
Boot drive – who cares as long as it does not also hold the OS PARTITION.