After saving the results from the deflicker, the visual preview process will start again, which is really resource consuming (especially if all cores are used during the process). So my question is: if we trust the deflicker work and we don't want to wait for the new visual preview and go directly to lightroom, how can we avoid the new (resource-expensive) visual preview process?

Just click again on "Visual Previews", it's a toggle button. This will stop them from being generated.