「後」か「後ほど」と「先」か「先ほど」
Which is the correct word to use when I want to say:

1) See you later
2) Just now...

For 1, I was told to use 後ほど instead of また後で.

Actually, what is the difference between the 2 words for each pair?

Question

「後」か「後ほど」と「先」か「先ほど」
Which is the correct word to use when I want to say:

1) See you later
2) Just now...

For 1, I was told to use 後ほど instead of また後で.

Actually, what is the difference between the 2 words for each pair?

Answer

I think 後ほど is more formal than 後で, maybe that's why you were told to use the former.
 
先ほで is more formal too, but if you want a word just like "just now" which including two meanings: "the moment just passed" and "right now" you can use "今(いま)".

Ne manquez pas cette occasion d'apprendre une langue depuis chez vous. Découvrez notre sélection de professeurs de langues expérimentés et inscrivez-vous dès maintenant à votre premier cours !