Mostly just Minecraft out of the box. I feel that resource packs and certain performance mods like optifine could be accurately referred to as “vanilla with optifine” or “vanilla with such-and-such pack.” Once you get into datapacks or Forge or Fabric or hacked clients, it’s not vanilla.
Serverside, it’s a little more dodgy. How many server plugins can you have before it’s not vanilla?
That said, I don’t think there’s much reason to play Java Edition over Bedrock other than mods or wanting to play on older, pre-bedrock versions. Then again, I almost solely play modded anymore so I don’t have a lot of vanilla Bedrock under my belt to compare the two.