Pretty similar to other engineering degrees, you just do a bit more breadth than usual to start with. Pretty close to mechanical (with the additional usually of some electronics stuff in first year) or aerospace (but with less emphasis on aerospace systems specifically) contentwise at least in the start of the degree.
Bear in mind quite a few "general engineering" degrees you will begin on a "general track" but specialise in one area later in the degree (e.g. Oxbridge, Exeter, etc). So you may well start more "general" at first but narrow in on a particular area later (which is pretty normal to do in any degree anyway as you figure out what your interests and strengths are).
Just read around your subject area, maybe look at taking part in science fairs/engineering competitions/hackathons and the like if you see any of interest. Some programming projects might also be relevant and interesting to you (you might particularly find them interesting if tied to e.g. robotics type stuff, which integrates a number of engineering areas).