For example, the sfx PSUs from silverstone and those from Corsairs, do they have the exact same dimensions like not only the length, width, and height but also mounting holes placements and etc?
Thanks in advance
SFX is a standard form-factor that describes all three dimensions, so all SFX PSUs will be the same dimensions and use the same mounting holes, but be aware that there is also the SFX-L standard which, while the same height and width and using the same mounting holes as SFX is a bit deeper to accommodate a larger top fan. (As far as I am aware, nobody has actually put out a standards document, but everyone has more or less agreed on it, so it's a de facto standard)
Low Profile (40mm fan) SFX power supply is nominally 100mm x 125mm x 50mm by this standard (Fig 34)
Std Profile (60mm fan) SFX power supply is nominally 100mm x 125mm x 63.5mm by this standard (Fig 41)
PS3 Profile (80mm fan) SFX power supply is nominally 101.4mm x 150mm x 86mm by this standard (Fig 43)
For the more recent PSUs marketed as SFX and SFX-L, they appear to follow the "Standard Profile" 63.5mm x 125mm "mounting face" dimensional requirement, including mounting holes, but measure 130mm (SFX-L) and 100mm (SFX) depth.
The mounting holes are going to be the same.
Any case that supports SFX-L will support an SFX PSU that's 5mm shorter, so it's fine. The problem is when it's longer which is why SFX-L is separate from SFX.