Rendered mode, first.
- Engine is Eevee by default, a quickie render engine.
- Cycles is the GPU/CPU-capable render engine.
- Preferences / System shows the render devices available.
- F12 is quick render.
- Samples: Viewport gets lower samples for speed.
- Render samples are higher to reduce noise, but there are limits.
- Layer panel, Denoising Data.
- Then in the Compositing view, Shift+A to add in Denoise module.
- Check "Use nodes" in top left corner (in compositor) and it will show up if the Composition view is "empty" after a render.
- Take output of "Noisy Image" and tie it to the Denoise module at Image.
- Then Normal to Normal, Albedo to Albedo, then Image output to Image over at Composite.