Can I install tiles or vinyl onto Gypsol screeds?

Yes.

You can lay any floor covering onto Gypsol floor screeds, including carpets, tiles, vinyl, LVT, and resin floor systems. As with all screeds, whether cementitious or Gypsol, they will need to be properly prepared; clean, dry, mechanically abraded, and primed.

The best practice is quoted by the Contract Flooring Association in their guide to contract flooring.
Also, any underfloor heating should be commissioned and run prior to installing floor finishes.