Manual focus is error free until your closeup vision starts to go… Then it's still often better than AF, but not necessarily error free.

It's only really needed on the earliest IS/VR/etc. lenses from the late 1990s and very early 2000s. Since then lenses are designed to automatically detect when they're on a tripod and turn IS off if it is causing a 'feedback loop'. Some Super Telephoto lenses even have IS modes specifically for tripod use, and leaving it on in that mode is beneficial.

It depends on your camera, how its shutter operates, and what specific exposure times you're considering. Assuming you use mirror lockup (or a mirrorless camera) and a mechanical shutter then anything shorter than around 1/100 or longer than 1 second will not be affected by shutter vibration. 1/100 and shorter is over before vibration from shutter movement reaches the lens. 1 second and longer are long enough that vibration from the shutter is not a significant enough part of the total exposure time.

So if the choice is between 1/160 or 1/80, up the ISO one stop to stay at 1/160. If the choice is between 1/2 second or 1 second, leave the ISO lower and shoot at 1 second.

” a compact mirrorless camera with a 24mm prime lens is far easier to keep stable than a heavy DSLR with a 70-200mm f/2.8 lens”

when the very weight difference is countered by adding even more weight to the camera, head, tripod say, underneath the combination to counteract unwanted wind, human or transferred vibration.
Similarly, whilest lighter carbon fibre tripods may be more convenient to carry, weightier aluminium tripods may have an advantage for this reason. Eaven heavier wooden tripods are often favoured for larger format camera outfits.

Similarly, the filters must be cleaned so that they do not accumulate anything that spoils the photograph. And from time to time, clean the sensor very carefully or take your camera to a specialized place to do so and get sharper photos .