Hello, extremely excited newcomer! We're happy to have you! I don't know that I have extremely detailed answers to all your questions, but I can at least give you some brief pointers.
As far as more vs less conservative, it depends on what you're talking about. The Irzali are definitely less so in terms of clothing, as they do tend to like eye-catching colors and patterns, love luxurious fabrics, and at least like to consider themselves quite stylish. This applies even to rural and poorer people -- they love to dress up to whatever degree their means allow. This aesthetic has rubbed off noticeably on big city Sirdabi, particularly among people associated with the court and anyone who wants to imitate them, but yes, overall the Sirdabi tend to be quite a bit less ostentatious. Orthodox Azadi does frown a little on ostentation, as it's seen as a display of vanity, and it's considered morally correct for wealthy people to dress modestly and spend their wealth on charity instead of selfish displays. This applies wherever you are in the caliphate, but ethnic Sirdabi are somewhat more likely to follow such strictures.
In terms of behavior, that varies too. Between the two Irzali society is overall a great deal more stratified, and has more restrictions in terms of what different classes of people should and shouldn't do. If you're a member of a noble family you can get away with a lot and don't necessarily have to display much respect for people lower on the social scale than you are. Unless you come from a particularly strict family you're also allowed quite a bit of leeway to do morally questionable things, like consuming alcohol or engaging in extramarital liaisons. People on a lower rung of the social ladder are supposed to show deference to those above them, and tend to follow Azadi morality more closely.
As far as being rebellious goes, that applies more to politics and governance -- Irzal province has been plagued by unrest and small-scale insurrection for most of the time that it's been a part of the caliphate. Most of the unrest comes from the high ranks of society, who feel a lot of nostalgia for the long-ago days of empire and dream of reclaiming their power and prestige. More popular uprisings typically come as a result of oppressive taxation or particularly callous behavior on the part of the caliphate's provincial soldiery. There have been a couple of major insurrections in Irzali history, but most such disturbances tend to be localized and ephemeral. Irzal originally became a part of the caliphate as part of a popular uprising against the empire's rulers, as the ordinary people were drawn to al-Azad's message of egalitarianism and equal justice and dignity for all people. Disillusionment later set in as the appointed governers of the province eventually became little better than the original rulers. So ordinary people tend to want to return to self-rule mostly as a way to return to the original teachings of Azadi and be less oppressed by anybody, whereas the upper classes want a return to self-rule so that they can reclaim their power and restore Irzal's former glory.
Birth, death, and marriage customs vary somewhat depending on where and who you are -- Irzal in particularly is extremely diverse. Most generally, marriages are arranged between the parents of a prospective bride and groom, sometimes with matchmakers or other go-betweens who might be relatives or friends ( either of the parents, or of the prospective couple themselves). The husband-to-be has to pay a bride price to the family of his prospective wife, the amount and nature of which can vary widely. The wife also typically brings some dowry of her own, whether it's clothing, jewelry, money, or livestock. Weddings are big affairs even among the poor, and a wealthy person's wedding could have hundreds of people at it. Food and money are also supposed to be distributed generously to the needy as part of a wedding.
Death is supposed to be low-key according to Azadi tenets, with heartfelt but dignified mourning and very modest markers for the dead. Sirdabi tend to be buried, whereas it's more common for Irzali to be cremated, but both bodies and ashes may be interred. Sirdabi corpses typically go straight into the ground with nothing more than a winding sheet, and may not even have their name inscribed on their marker. But this is the ideal, which has tended to be eroded over time. Once again, Irzali are usually more ostentatious than this, and may have very elaborate grave markers, urns, and tombs or niches to keep the urns in. Even modern-day Sirdabi now tend to have "real" headstones, and holy men and women often have mausolea which may also be associated with a mosque, school, or hospital.
The life journey of either a Sirdabi and Irzali can once again vary a lot depending on where they live and what social class they belong to. People are generally expected to receive at least a modest education, get married and have a family, and contribute constructively to their community in some way even if it's not through paid work. Most children throughout the caliphate learn to read and write. Children from families of small or middling means can go to free schools in towns and cities, where they receive instruction in reading, calligraphy, and the Perfected Song of God. Traveling teachers also visit smaller communities seasonally to teach these things. Wealthier and noble families don't usually attend primary schools like this, but instead will have private tutors. But sometimes even upper class children will attend a school part-time if the teacher in it is especially renowned and respected. Young adults may attend a madrasa to receive a higher education. Although more common in wealthy families, even the poor can receive a charitable scholarship if they display sufficient ability and/or can get a patron to sponsor them. University study can begin at around 16 and continue indefinitely, depending on what the student (or the family) wants from their future.
There is an ancient religion in Irzal: Elestaari. Elestaarians worship the God of Good Thought, and have many rituals involving fire. Wedding ceremonies in Irzal still reflect this -- the bride and groom affirm their vows while holding hands over a brazier, and they must also jump hand-in-hand over a fire to complete the wedding ceremony. Elestaari was the national religion of the Irzali Empire and often served to focus resistance against the caliphate in its early years, so the religion was very strictly repressed for quite some time. In the last couple hundred years restrictions against Elestaari have eased but most Irzali have remained Azadi. There is still a strong core of belief, though, and Elestaari has regained its significance as a symbol of Irzali patriotism. But not all Elestaari favor independence from the caliphate. There is a little bit about Elestaari and the God of Good Thought on the Religion page on the wiki.
I know this didn't answer everything, but feel free to ask for more specifics! Also, given the variety of practices you could potentially find across the caliphate, you're free to use historic Arabic/Persian culture as inspiration for particular details in your story. 
