Welcome to this forum, and great that you consider purchasing TG. A new world will open to you, and any help needed can be provided here.
I don't use heightfields, but mainly work procedural, so I'm not really the one to answer this, but I think 1k is not really a problem, unless it's a huge area you're covering. And if you add more displacement fractals, any 'softness' of the heightfield can be camouflaged.