Raws Details – Use it or not?

Well then – many thanks for all responses. Meanwhile I realized that my questions in way were superfluous as "Raw Details" are executed automatically when denoising a picture. 
Remains the (minor?) question as to whether increasing or decreasing the %-value of denoising does have an impact on the RAW Details - processing as well.
Also I noticed that LrC is crashing more often than usually, if I perform denoising for several pics (e.g. 10 at a time) using the "automatic synchronisaton" feature. Maybe this has to do that I'm running an older PC with only 8 GB RAM available. (A newer PC should be available soon). Or it may have to with the fact that all my data is on external disks and the connection is not stable enough(?).

Your question seems to really be how many pixels do I need in the final exported image that you will use on those other display devices. That should be based on the pixel dimension of the device/TV. 4K TV is actually 3840 x 2160. Any greater pixel dimension of the image you want to display on that 4K will just be lost in the reinterpolation for the screen size.

If have deeply cropped an image and need more pixels that might be the time to use Super Resolution.

Think in Pixel dimensions, not DPI. DPI is more commonly an issue in printing and doesn't apply to displays. (except as part of the specs.)

Since 4K TV is 3840 x 2160 your photos will fit best if you can crop them to that ratio during processing in Lightroom Classic.

That's a 1.777 crop ratio.

I have used all the detail features over several years as they are enhanced, in the past two years there have changed significantly and created challenging workflow issues for users.

These features were a great assistance to me when preparing images for large sized prints at professional labs.

To determine if Raw Details improves the image, apply it, and then compare before and after at 100% view.

If it improves the image, keep it, if not, don't use it.

Viewing at 100% is extremely important for assessing any image detail. This is the only magnification that gives you a true impression of the image – one image pixel is represented by one screen pixel. Any other view (like Fit) will be inaccurate and misleading because the image has been scaled.

If you have a high resolution monitor (generally 4k or more, but less than that if you have a laptop), you might want to use 200% view because the pixels are tiny, and details that you cannot see at 100% may be revealed at 200%.

I have tried Raw Details from time to time over the years, but I have only seen a marginal improvement in a few cases.

Most of the time, there is no visible change in the image, so I never use it.

It might be useful in combination with Super resolution, which I don't use either.

To determine if you should use it with Denoise, create a virtual copy, do Denoise on the original and Denoise + Raw Details on the virtual copy. Then compare the results at 100% view.

Contrary to what the name may seem to suggest, 'Raw Details' does not increase the general amount of detail, so it is definitely overkill to use it on each image. Raw Details uses a different kind of demosaicing that can give a rather subtle benefit in certain images, such as an image that contains a neon sign. In most images you won't see any difference.