https://vitamindwiki.com/ is a useful aggregate site for papers (peer-reviewed and others) on vitamin D. The latter is cholecalciferol (https://en.wikipedia.org/wiki/Cholecalciferol).

https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessiona... (excellent series for all vitamins)

Different manufacturers = varieties? It's the same stuff or should be.