Neither. There is no such thing as a “religion of peace” or “religion of conflict”. No religion is either. Islam is simply a set of religious beliefs and identity. It is an Abrahamic monotheistic religion. One that has almost two billion followers in the world. Contrary to what many people seem to believe or try to promote, Islam is not a monolithic belief system. There is a great deal of diversity within the religion itself. Something that is often not visible to outsiders. Different groups of Muslims interpret Islam and its teachings in different ways.
There are those who believe that Islam teaches Muslims to not hurt others and to stand against tyranny. Then there are also those who have quite a violent interpretation of Islam and use it to justify violence. As well as many interpretations in between. Or completely different interpretation altogether.
Religion is simply a set of beliefs or an ideology. It isn’t really inherently violent or non-violent. The same applies to Islam. Its interpretation depends on the group of people. It is ultimately the followers of any religious group (or ideology in general) who decide exactly what the ideology stands for or represents. So it is the Muslims themselves who decide by their actions or beliefs whether Islam is a “religion of peace” or “religion of violence”.
How can we possibly compare the belief system of the Sufi mystics with those of groups like the Taliban or ISIS. Both believe in the same religion. Yet, there is a wide gulf that separates their different interpretations of Islam.