Packs are primarily moving via the traditional supply chain of beauty supply stores. They are done by large companies which are using non-remy hair and selling it in packs as brands. The hair quality in packs is typically cheaper compared to virgin hair.
The hair industry was earlier primarily using Kanekalon fiber and later slowly incorporated multiple products. This industry than slowly moved to china with cheaper Chinese labor. The retail stores selling pack hair were still controlled by Koreans. Over time, the Chinese started opening small companies of them and used channels like Ali baba and Ali express to sell bundles and small quantities to USA creating an alternative supply chain.
Earlier the quantity of bundle hair was better compared to packs as the cost of supply chain was lower. While both the supply chains primarily supplied non Remy products, the quantity ratios were better in Bundles. Thus, the cost of bundle hair per piece was lower compared to packed hair.
The alternative source of bundle hair is India where few select companies like Natural Indian Virgin Remy Hair Wigs or Extensions started marketing of virgin hair as bundles but building their overall brand outside of the retail supply chain. This hair sold as bundle hair primarily goes to hair stylists and salons that rebrand and sell it as their product. Lot of hair stylists and salons join the partner or wholesaler program Wholesale Hair Extensions: Indian hair manufacturer Indian Hair Vendor and resell the hair. The advantage of the bundle is that it is a White Label product and can be resold as individual brand.
So while there is no clear quality difference between bundled hair and packed hair, sourcing it correctly from right supplier of bundled hair can allow hair stylists / salons to build their own brand. While doing it wrongly and going to ali express etc, can ruin their brand reputation.