@MHants1999 there’s some advice on here that you need to sift out and ignore from people who haven’t read engineering and have never worked in the industry.
I faced a similar dilemma at your age and chose the Sappers but have also had several years in industry too. I am a Chartered Engineer, and have mentored Graduate schemes and sat in review panels. So here’s my advice.
If you want to be an engineer, get the best degree you can achieve. Go and get a post/graduate cadetship with the best civils company you can find, one with a proper program for mentoring and a track record of developing young engineers. Work on the biggest, most complex civils projects you can get on and push hard to get yourself chartered.
Join the Reserve to get your fix of soldiering. Again, go for the best; challenge yourself with Paras, SF or whatever and get commissioned. A Reserve commission can really speed your route to chartership by givIng you management experience that can be hard to get as a junior engineer. By far the biggest push back at Chartered Professional Review I saw was lack of management and leadership experience.
If you want an Regular Army career, it means compromising your engineering career whatever you join. The Sappers May be everywhere, they may have roles ranging from professional engineers right through to Commando and Para. But don’t let them kid you that they do much of the proper, real, complex engineering that will satisfy someone who is truly a vocational engineer. Sure, you can get Chartered but your CV won’t have any real projects of substance. Perfectly possible to get good jobs in the industry after a Sapper career, but they will almost certainly be project management roles, not senior engineer roles.
Join the Infantry or Armoured Corps for anything more than 3-5 years and you will pretty much say goodbye to a real engineering career. You will find it very difficult to get into an engineering cadetship scheme five years after graduating. Doesn’t stop you getting into the project management side of engineering of course, but you’ll be way behind your contemporaries.
My last thoughts; you don’t have to make a decision yet. You may find that after three years at Uni an engineering career isn’t that attractive. I know several people who walked away from engineering completely and never went back, some of whom going on to very successful service careers and never touching engineering again.
On the other hand, you might be so fired up by engineering that you no longer countenance the thought of compromising your engineering career to join the infantry.
I think you’ll know the answer when the time comes. Meantime enjoy University. And do something (lots of things) there that widen your horizons; engineers can be very dull people!