OK, these comments have convinced me that highway=path is the most appropriate for hiking paths, at least in Scotland. Thanks to everyone who responded to my query. I will update my edits to reflect that later, and for now I'm taking a forced break off OSM, due to rain having caused my GPS device to die.

Thanks and sorry for the double-post confusion ;-)

Thanks for the clarification!

In situations like this, when you have better data than the original, just go ahead and edit, it's unlikely that the original author will have a problem with it. I find that (at least in some regions?) the aerial photos are often misaligned, before doing any tracing it's best to make sure that the image is aligned with existing features on the map and if not, then align it manually. This is probably the source of the lake's misalignment, no big deal.