Throughout GCSEs (I'm now an A-Level student but check this sub) I was often the token "marmitecake understands it, ask her for more help" kid. I achieved great grades but always woke up in the morning thinking "is there any point in me going in today?" because the majority of my teachers weren't very motivational or inspiring, honestly.
What I found the most motivating was when my teacher went slightly off topic to something current and interesting, sometimes sacrificing 5-10 minutes of concentrating on a curricular topic can motivate students for the next 60, 80, 90 minutes. Injecting a bit of yourself to your lessons, making inside jokes with students and classes, anecdotes maybe, can make students feel like you genuinely care for their success and make them work harder and enjoy your lessons too. Another thing that motivated me personally was independent, self-guided learning, however it is very risky to trust students to do that because a large number won't stay on topic, but for those who you can trust to do it, I think it's definitely worth doing.
In relation to pairing a stronger student with a weaker one - it completely depends on if they get along and if you think that it will be beneficial for them individually. For instance, putting the class shut-in with 9's across the board with the class clown working at level 3 isn't going to work at all, and some students can take it as a bit of an insult when you put them with someone "better than them". It really depends on the students. In my classes at GCSE, most people I was "put with" had no interest in actually listening to me or, in fact, learning at all, and so it was a waste of time. But for those who did want to improve, did want to listen, and did want to learn, it was greatly beneficial. I also think if you do this you should make sure the "better" student 100% understands whatever they'll be "teaching" because if not it can make them get much more confused and essentially move backwards.
I'm also not at all a qualified teacher but one thing that worked well with badly behaved students in class was to break things down into much smaller steps, rather than one big thing. One big, massive topic or task can seem like such a drag or such a "waste of time" because you're spending so much time on "only one thing" that they won't even start it, if considering starting at all. Sometimes not mentioning the larger topic or larger task can make it seem less daunting. If you have to write 6 paragraphs for an essay, don't mention the whole essay, mention 1 paragraph at a time and "celebrate" (do something else unrelated to the essay) inbetween each one. Also, just generally being up for a laugh and joke can go a long way, find something to make you "cool", maybe window or table pens for those who want to use them. Maybe a game with the contents of the past topic every few weeks with sweets as a reward. I always think pupils should have the choice to participate in these though - some don't want to and they may be better off doing something else.
I hope that didn't sound a mess or pretentious etc. in any way, just sharing some of what I saw help in my high school.
Good luck!