When it comes to Java there are very few people who would fall under the definition of playing “Vanilla” Minecraft. Almost everyone uses Optifine or Sodium. I would also say that using any resource pack still counts as vanilla, as long as it isn’t X-Ray. I would define myself as a mostly vanilla player but I feel like the mostly vanilla devinition is very gray. Some people would say using things like sleeping bags, backpacks, minibosses, and/or extra inventory utilities would be mostly vanilla.