My advice would be to focus on getting a 2.1, and anything above that is just icing on the cake.
A 2.1 with extracurricular experience, internships (and a good research record if you want to go into academia) will go much further than a 1st. Focus on getting those things after you know what you need to do to get to a safe 2.1, then once you can do those things, look into how to get a 1st.
That said, it's also a lot easier to get a 1st at some unis than others, e.g. some unis will have 50% of MEng students graduating with a 1st, others will try to limit it to 30% or below.
I'd also disagree with afghanambition, it's much easier to get a 1st in Engineering than in Humanities. For engineering there are specific right answers, whereas for Humanities this isn't the case. As a result, humanities results tend to be clustered much more towards a 2.1, it's not uncommon to see courses with 70%+ getting 2.1s in arts and humanities. This makes it a lot easier to get high marks in engineering.