I know that it is all very well pontificating about stuff like this, and without some work to back it up an opinion is just that – an opinion. So I will try to explain myself a little further by using the two example pictures attached below (leaving to one side whether they have any artistic merit or not, and just treating this as a technical exercise).
The wind turbine shot is what I would call a typically strong B/W subject, where colour would add little to the finished print. There is clearly directional lighting, low and quite dramatic, and plenty of contrast with well defined edges to the main compositional elements. This type of subject, converted to B/W, will stand a lot of manipulation, both spectral and luminance adjustment, without falling apart. There is very little in the way of subtle half-shadow areas which are always subject to noise, and the light was strong enough to use a low ISO (100) even handheld. I wanted to dramatize the sky without using a grad filter in LR (otherwise the top turbine blade would have darkened), so I applied a home-brewed orange filter to the whole image. Inevitably, this increased colour noise, but its effect was restricted to very small areas and a setting of about +20 NR pretty much eliminated it.
The oaks in fog was a wholly different matter. This was shot in very low light at ISO 400, which on the ‘Blad is pretty noisy anyhow. The picture is totally dependent on extremely subtle transitions between delicate shades of grey, with no true black or white in the image, and is of inherently low contrast. This photograph will not withstand heavy spectral manipulation without becoming excessively noisy, because most of the tones are in the precise range where noise will be most apparent. So in this case I converted the original to B/W using an absolutely flat grayscale (desaturation would work as well), and made all my subsequent edits using luminance adjustments only. Finally, I removed the small amount of colour noise that was inherent in the image, but left the luminance noise to provide some texture to the final print.
Lightroom actually provides all the tools that you require for very sophisticated editing, and once you have mastered them you can then benefit from a deeper understanding of the principles behind B/W imagery. And that, in the long-term, is very much more rewarding than the one-size-fits-all approach of using someone else’s presets.