Takže aby bylo jasno:

https://www.upgradeable.com.au/pages/mac-mini-ssd-upgrade-guide

Is the SSD the same physical size as my current hard drive?
Yes. The standard Apple Mac Mini 2006-2012 hard drives are an industry standard 2.5 inch notebook drive. They are physically exactly the same physical size.

Can I use any SSD here to upgrade my 2014-2019 Mac Mini?
No. From 2014 the Apple Mac Mini SSD was a proprietary NVME SSD. The 2019 Mac Mini SSD was soldered onto the motherboard and can not be removed or upgraded.

Does the 2014 Mac Mini use a standard M.2 SSD?
No. It is only standard in it's physical size. A standard M.2 drive will not work. Apple has made their drives proprietary.