Re: how is these skincolors and texture done in ps
Getting pores and texture shouldn't be too difficult with any newer generations of "full frame" dslrs or digital backs depending on subject size in the frame If you want more pronounced texture in that regard it's probably easiest to achieve by adding sharpening when doing your file processing. Some of the other methods you mentioned can work. They didn't appear to be done in an identical manner to me. You can do stuff like add unsharp masking, high pass filter, etc. with a wide radius masked to primarily hit the shadows (I think this is what you're referring to) but I'd definitely put on a bit of capture sharpening to get the pores to stand out. Some of the fine tuning is the kind of thing I'd play with a bit if I was asked to do this to an image myself. It's not always an exact formula. If you're using natural light make sure you use a tripod.
On the guy in the suit, the original framing may have shown the man much larger to maximize detail captured. The background was probably photographed flat with the framing much tighter around him. Adding in the background around him after would be the optimal method for maximum skin and clothing detail. The skin and the clothing look like capture sharpening + maybe a slight boost to the midtones and maybe a couple touches of unsharp masking selectively on a few details. Wide radius sharpening in photoshop isn't always bad. It's just that most people way overdo it. It doesn't work well for anything beyond a mild boost. The background in this photo was probably adjusted darker/color corrected green in post.
The chef picture I'm not 100% sure. Could have been shot that way. It was most likely set up not to be too saturated when processed. If they dropped in the background they did a nice job. I don't see as much obvious heavy sharpening as the first. It's a bit further back so skin details aren't as heavily pronounced.
The guy in the field every element is processed warm obviously. He looks very cut out to me. The photo is in a panoramic format. He could have taken as many frames as he wanted to create the fields. Done properly you can get insane detail from photo stitching for backgrounds. Combined with sharpening you can get that kind of detail for those foreground/background elements. The sky may or may not be dropped in. I think the tractor and the man are dropped in there. The man could have been photographed much larger which would've given him a lot of detail to work with on the man too. All of those elements appear to be processed out warm or adjusted to look that way. The softer light going through the crops from the left appears added in post. There are a few ways to do that via filter lighting effects or an adjustment layer. You'll need some masking. The finer bright crop highlights look like they were created with some selective sharpening. Not to say it's 100% done by sharpening, but the border definition on those highlights suggests it. You'll need to play with radius and amount to get it just right. I won't get into the debate on the different ways of sharpening in photoshop. Some of them are less destructive or offer more control but any of them could get you there.
Does this help? Just make sure you don't 100% rely on sharpening. There is some capture sharpening, but a lot of what I see is being used to accent details. Bah that took way too long to write.