[rusculture]

My point is that Theravada teachings seem to be at odds with the Nikayas.

I want to understand IF vipassana is an actual meditation practice taught by the Buddha or not and if the Kasinas are or not, etc.

Theravada teachings are not at odds with the Nikayas they are based on the Nikayas. I find it strange you think having a few extra meditation techniques makes us "at odds".

If you read the Nikayas you will note they are not a meditation manual and contain general guiding principles on mental cultivation/meditation.

The pali word Vipassana is not the name of a meditation technique in the Nikayas but means clear seeing. However nowadays meditation techniques designed to bring about vipassana are generally called (or even branded) Vipassana meditation in much the same way that exercises designed to bring about fitness are called fitness.