「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)".