Almost, but not entirely.
First and foremost, it all depends on the asset and its thresholds on the UV map.
For example, sometime clothing assets from SuguP are constructed even on a few pixels
Each asset has different pixel thresholds.
One might have 2k, another 512, another 1024, another 256, etc.
This is an individual matter.
You adjust the size to whatever parameters allow you without losing detail.
Relative, dependent, on the author of the orginal asset.
Becaus even pixel sizes that are too high can result in loss of detail. For example, YueFengYu's mods from Date A Live implement 8k, which makes details blurry/pixelated. 1k/2k are the appropriate settings.
I wouldn't suggest not messing with the detail mask normalmap normaldetailmap color mask, etc, it also affects many factors, such as changing details or simulating, for example, cellulite on the body.
Especially if your example is the projects from that idiot moegelerattio (this guy has no skill, puts 4k everywhere, and creates a Frankenstein without optimization, he doesn't know any fundamental knowledge).
For example, in all the hair assets on his cards, you can reduce the color mask to 1x1-8x8-64x64 pixels
and the detail mask to 64x64-256x256 pixels
(now imagine if 40x hair elements have implemented 512 to 2048 pixels, when they don't have to, or even imported 4k).
The overlay size is also relative.
It depends on what you want to achieve.
If the overlay is a only solid color, you can even use 1x1 pixels.
For excampe:
orginal
With 1x1 pixels:
You're also spreading false myths about alpha mask.
You're prioritizing MainTex, and any other influence is the shader type, plugin.
Alpha mask is rarely required for interference.
It is mainly used in situations where white lines remain in the perimeter when remodeling an asset.
More often than not, people overuse this feature.
And what's worse, alpha mask can have different thresholds than maintex.
This sometimes requires larger dimensions than maintex.
You can also use the Overlay plugin instead of MaterialEditor.
For example, on clothing.
Anyway
I've been creating mods using Photoshop for many years, and I can tell you from personal experience that most of the projects from people in the koikatsu community need at least some fixing.