What are the differences between joy (piti), bliss (sukha) and peace (santi) and how do the qualities relate to Nibbana? This is a follow-on to this question 

What's the connection or difference between joy (piti), and the "bliss" (sukha) and peace (santi) of Nibbana?

Is one required to seek joy to attain Nibbana? Why? Should one seek sukha, peace, or Nibbana (to attain Nibbana)? If Nibbana and joy are different then why is (or what's meant by saying that) joy is one of the path factors?

It seems to me the meaning of the English words "bliss" or "happiness" is synonymous with "joy" so why does it seem like Nibbana has been described as "bliss" or "happiness"?

In my opinion if there is no element of "joy", "pleasure", "delight" etc. to the attainment of Nibbana then it  is wrong to refer to it as "happiness" or "bliss". 

I don't understand how it could be possible for there to be an unconditioned happiness or bliss.
OP: What's the connection or difference between joy (piti), and the so-called "bliss" (sukha) and peace (santi) of Nibbana?

Piti and Suka are encountered along the path arising due to the practice of concentration.



(Ekādasaka) Cetanā’karaṇīya Sutta Introduction by Piya Tan



(Dasaka) Cetanā’karaṇīya Sutta Introduction by Piya Tan

OP: Is one required to seek joy to attain Nibbana? Why? Should one seek sukha, peace, or nibbana? If nibbana and joy are different then why is (or what's meant by saying that) joy is one of the path factors?

These are milestones along the path. One does not seek them but you naturally pass them when practising, similar to when going on a road trip to a city you pass many mileposts. 

OP: It seems to me the meaning of the English words "bliss" or "happiness" is synonymous with "joy" so why does it seem like Nibbana has been described as "bliss" or "happiness"?

When translating authors choose English words to map Pali terms into. Many of the English words are no perfect matches. So one must try to understand the actual meaning in the disclosure's context.

OP: In my opinion if there is no element of "joy", "pleasure", "delight" etc. to the attainment of Nibbana then it is wrong to refer to it as "happiness" or "bliss".

Feelings of pleasantness, unpleasantness and neutral feeling are not entirely satisfactory.

Also, also bliss or joy born from meditation also changes when one loses concentration hence they are not satisfactory.

Nibbana is happiness or bliss, not dependent sensations or any other form of support. Nibbana is beyond space and time (cosmology) and psychological phenomena.


  For the sake of discussion, we can imagine—since we have not attained nirvana—that the first paragraph [§4] addresses nirvana’s freedom from space and the second paragraph [§5] its freedom from
  time.


Nibbāna Paṭisaṁyutta Sutta 1 Introduction by Piya Tan