What 'closed' can mean
The word covers several different situations. Initiatory: entry is by initiation within a lineage, which includes Gardnerian Wicca itself. Community-held: the practice belongs to a people and is learned within it. Oathbound: the material exists but its holders have undertaken not to share it. Restricted in part: outsiders may respectfully participate in some things and not others. 'Closed' is not one rule, and communities are not unanimous.
The questions worth asking
Where did this actually come from? Is it part of a living tradition with people currently practising it? Is initiation, lineage or community membership involved? Are practitioners from that tradition themselves teaching outsiders, and on what terms? Am I keeping the context, or stripping it? Am I renaming someone else's practice as Wiccan? Would I be comfortable describing what I do to someone from that tradition?
Smoke cleansing, sage and palo santo
Smudging refers to specific ceremonies of particular Indigenous North American nations; it is not a generic term for burning herbs, and using it that way erases the tradition it names. White sage carries both appropriation concerns and real wild-harvesting pressure. Palo santo is protected in parts of its range and commonly mis-sourced. Rosemary, bay, garden herbs or ordinary incense will smoke-cleanse a room perfectly well.
African diaspora religions
Hoodoo, also called conjure or rootwork, is African American folk magic with roots in the enslaved South, distinct from Wicca and taught within its own communities. Haitian Vodou is a religion with priesthood and initiation, and is not the same as Louisiana Voodoo, and neither resembles the film version. Santería, more properly Lukumí, is an initiatory Afro-Cuban religion. Brujería is a broad Spanish-language term covering many distinct Latin American practices. These are living religions with living practitioners, not aesthetics or ingredient lists.
South Asian material
Chakras, yoga and karma come from Hindu and Buddhist religious and philosophical traditions with long textual histories. They arrived in Western occultism largely through the Theosophical Society in the late nineteenth century, already substantially altered. Using them is not automatically wrong; using them while pretending they are generic spiritual furniture, or while getting them plainly wrong, is disrespectful and also just inaccurate.
Runes
Runic alphabets were writing systems used across the Germanic world. Divinatory use is attested only thinly in period sources; the systems sold today are largely twentieth-century reconstructions. Bindrunes as personal sigils are modern. Heathen and Norse Pagan practitioners have their own well-developed traditions and are worth reading before borrowing. Be aware, too, that some runic symbolism has been appropriated by far-right groups, which is worth knowing before you wear it.
'Celtic Wicca' and the Celtic question
Modern Wicca uses Gaelic festival names and Celtic-flavoured imagery, but historical Celtic religions are known mostly through archaeology, hostile classical writers and later Christian-era Irish and Welsh manuscripts. Celtic Reconstructionist Paganism and modern Druidry are separate movements with their own approaches. 'Celtic Wicca' usually describes Wicca with Celtic decoration, which is fine, as long as it isn't presented as continuity with Iron Age religion.
Explaining is not teaching
Pretty Little Wiccan will describe what a practice is and where it comes from without providing instructions for it. Knowing about something and performing it are different, and the first is always available to you.