Can I play AMFP without having played TDD?

[Googolplex]

If Frictional Games had developed their own sequel to Amnesia like they had SOMA, whatever Amnesia 2 would have been named, it would have been a hell of a lot better than AMFP.

Absolutely play The Dark Descent first. It is wholly and truly the Amnesia package, with sanity, inventory, plates that you can throw against the wall, etc.

Amnesia 2 would be the worst name for a sequel. I generally hate numbers in names. But yes, TDD is better and scarier, but AMFP has the best story of all video games and the atmosphere is also quite good.