Lottie/Zach come across as a quite likeable couple, the kind of people you could meet at a party and chat away to without even knowing them too well. They seem like an atypical couple in their 20s; not saying we all should feel the need to be out exploring constantly, but they appear quite open minded/interested to learn about the world around them. Sort of the exact opposite of Zoe/Alfie, the sort of people who trap you in a corner and you have to fake needing a piss just to escape their tedious, self-centred chat.
Side note - this has been mentioned before, but I feel like Jim would be a way better match for Zoe than Alfie. I haven't watched tonnes of his content but he seems way more mature and grounded. I can imagine that he'll settle down and have a family soon, unlike Alfie who will blatantly just use the baby as a fashion accessory and then forget to do basic tit like feeding it/changing its nappy.