Hi, welcome to Lightroom Forums!
Some background (some or all you may already know):
Because of the way that Lightroom does business (parametric editing process) anything that is done can be undone, either in part or in full.
What this means is that applying any preset does not harm any image, so, if that preset is not correct (howsoever defined) for the situation its effects can be removed.
For the same reason it doesn't matter particularly in what order edits are applied (This is very different when using pixel editors such as Photoshop - although some editing does approximate parametric-type editing in Photoshop these days). Whatever order edits are done in the Develop module Lightroom will actually apply them, when producing a derivative image, in an order that produces the best result.
Presets are best applied in situations where specific characteristics of an image are already known and don't tend to work well when applied indiscriminately. IMHO this applies especially to sharpening and noise reduction.
Sharpening and noise reduction are two sides of the same coin. Sharpening not only affects the noise characteristics of an image but applying noise reduction also affects sharpening. As a result they have to be viewed together. In fact the luminance noise reduction slider should be viewed as the fifth sharpening slider (the colour noise reduction slider almost never needs to moved off its default setting).
A full exposition of how the sharpening and noise reduction sliders work is well beyond this post. However, it is absolutely true to say how one applies sharpening (read sharpening and noise reduction) settings is extremely image dependent. Technical factors such as ISO and other exposure settings are important. No less important is the subject matter of the image as well as one's aesthetics.
Generally images with a high edge frequency (such as a detailed landscape image optimally focused) is approached very differently to an image with a low edge frequency (such as a portrait of a good looking woman with a flawless - or perhaps not so flawless - skin). Applying the same settings to both sorts of images will lead to at least one visibly suboptimal result.
So far the discussion has centred around what is referred to as capture sharpening (and noise reduction). However, sharpening also incorporates what is referred to as creative sharpening and output sharpening. How these are applied also depends on all the image details outlined above and the degree to which capture sharpening has been applied.
Perhaps the best way to summarise how presets should be viewed is to emphasise that applying presets is never a substitute for understanding the effects of the settings that comprise the preset. Otherwise, whether the result is a good one or not, one has no real idea how that result was achieved.
That said I do use presets for both sharpening and noise reduction - these are specific for lens type and focal length, ISO and exposure, and subject type - and even then images are often further edited to fine tune the result.
Two of the best resources that I know to learn image editing in general, and sharpening/noise reduction in particular, are the "Camera to Print and Screen" series available on the Luminous Landscape website and George Jardine's offering available on his website. I have no provided links but either site is easily found via a Google search.
Tony Jay
