Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
If the character and religion of this man are not pleasing, then there is no harm to break this engagement. What we advise you with is what the Prophet (Sallallahu Alaihi wa Sallam) advised in the Hadith, reported by Tirmizi and others, that Abu Hurairah narrated that the Prophet (Sallallahu Alaihi wa Sallam) said: "If a person with whom you are pleased regarding his conduct and religion proposes to marry one of your females, then marry him, otherwise a Fitnah (temptations and corruptions) will spread on earth and a lot of mischief will occur."
Regarding wearing Niqab, please refer to Fatwa: 85567.
Allah knows best.