I need your advices for inseparable

You see, I plan to offer my little sister some lovebirds, but I would like to know a couple of things before being totally sure about buying some. First, is it safer to get two males, two females, or a male and a female? Then, do they get scared quickly or are they birds that are not very afraid of humans? And finally, are they the kind of birds that require a lot of care? We have time to monitor them and take care of them at home, but I want to be sure that they are not birds that require intensive needs. Thank you for your help

https://preview.redd.it/ck5bbz1oyvqe1.png?width=600&format=png&auto=webp&s=0dac3c583220bad369e55f25336f400b691cc87e