In the past (years ago) I would sometimes miss some prayers and intend to make them up but I would not make all of them up sometimes. After repenting, is there anything that can be done now (in terms of making up) according to the most authentic view? If I make up, how should I do it?

There are two sayings and both are strong, one that you make them up and one that there is no qadaa and you repent and increase in good deeds, and repentance is a must either way. If you do make them up then do not pair one with each prayer, string them together, keep the order between the five, and act on the number you think most likely, as Imam Ibn Baz said.