Well, I now got a little more free time so here’s a short answer and a long answer:
Short answer: No. Researching real-life ‘magic’ for fiction isn’t sinful.
Long Answer: You’re just looking up the lore and fictionalizing it. That it in of itself does away with anything that makes it occult. The rationale of the Church’s condemnation on the occult is the First commandment. We are not to have any other supernatural recourse but God. We don’t call to ‘spirits’ or other gods. We are to worship one God and that One God alone.
When you’re fictionalizing the lore of ‘real magic’ for fantasy, that does away with anything involved in that kind of worship. For example, Dante borrowed heavily from Greek and Roman myth but that doesn’t make him a pagan worshiper. He’s not worshiping anything. He’s just taking the elements of myth and incorporating it into his own work.
Regarding the different kinds of magic, the difference between fictionalized elements and the real occult only get sharper. This is because different ‘styles’ of magic in fictional settings have their own way of being different from the supposed ‘real-life’ counterparts.
Let’s use your examples:
In reality - It’s a complex, destabilized belief system. Different tribes have different takes on myth. Rituals can be just as diverse. That’s even assuming they managed to preserve their traditions for a long time. My professor studies these cultures in respect to our country. Even today, he and other researchers struggle with uncovering what little material we can gather on pre-colonial folkore. I would assume a similar situation faces other tribal, pre-colonial forms of shamanism (voodoo as well, if NatGeo and Wikipedia are any indication).
In fantasy - Shamanism in fantasy is usually characterized by its primitive and tribal aesthetics. Animal skins, bones, raw catalysts like plucked berries and ground herbs. These are all used at some point with the power of shaman-type characters. These same characters also emphasize harmony with nature. As such, it’s not surprising to see some of them possessing strong affinities with animals. The use of totems are another prominent feature. As for combat behavior, they’re a varied mix of warrior, healer, beastmaster, and spellcaster.
In reality - Correct me if I’m wrong but I’m guessing you’re referring to the fictional depictions of religions like Taoism, Shintoism, and maybe even Buddishm and Hinduism. In case you don’t know, there’s a lot of disparity between the philosophies of these religions (some even have different schools like Buddhism) but are barely really touched by their fantasy counterparts (as far as the magic itself goes).
In fantasy - From my experience, ‘Asian’ is most often Oriental. You have Japanese mikos, Korean ‘shamans’, and Chinese sages. Asides from their distinguishing appearances, they usually use items like beads, paper talismans, staves, and sometimes even the swords of their respective countries. Magic for them is actually not much different from western magic though it does delve into communing with spirits and nature. Gestures tend to be aesthetically different as well (e.g. Japanese hand seals) with different language and symbols. The energy they channel is also different (mostly dubbed qi, ki, or chi with both physical and mental prerequisites to channel properly).
In reality - Much like shamanism, things like Wicca and neo-paganism are no more an organized system of beliefs than they were years ago. Although, there is also an equally high fixation with nature worship, environmentalism, spiritism etc. It’s also strange that they use herbs and incense as much as their shamanistic counterparts. Why this is is all strange can be seen in the extremely sharp contrast with fantasy.
In fantasy - Magic IS science and is usually powered by a fictional energy source (mana being a commonly used name). This is perhaps the strongest point of contrast. In popular fantasy, the arcane arts do not require worship but extensive study and mental training. Apprentices and masters alike practice their crafts within the confines of secluded castles or prestigious academies. Wizards are usually depicted as braniacs, familiar with the mechanics behind mystical forces. When compared to shamanism and at times, Asian magic, it makes heavy use of civilized tools (ranging from simple wands and staves to guns and mechanical constructs). It’s like the difference between an organic farmer who likes things all raw and fresh as opposed to a genetic scientist that dabbles in artificial manipulation and advancing technology. Themes between it and science fiction are also quite similar. For example, the powerful nature of magic is discussed in a manner not that different from how real scientists debate over the proper use of dangerous tools like nuclear technology.