Gtx 1660s or rtx 2060?

I wanted to ask which of the above cards is better and whether 6 gb is enough (I mainly play Minecraft)

Yes, both are sufficient for mc.

I would still take the 2060

But preferably one from the 3xxx series

The 2060 is better. The 1660s is also thick enough for Minecraft.

Both of the graphics cards are sufficient for Minecraft. And 6GB of graphics card memory is definitely enough. If you play Minecraft without a shader, 256 MB of graphics card memory would be enough.

The RTX 2060 has more power than the GTX 1660 Super. 6 GB VRAM is sufficient for gaming on Full HD. WQHD would also work.
The performance of the GTX 1660 Super is easily sufficient for Minecraft. Then the processor and RAM are also relevant.