Materials are available in up to 8K - sometimes even larger than that. All textures come with PBR maps and tile seamlessly.
Photogrammetry is used for many new materials - ensuring accurate displacement maps down to the pixel level.
Many materials come with Substance (SBSAR) files that allow you to tweak them to your needs.
Assets from ambientCG are available under the Creative Commons CC0 Public Domain License and may be used for commercial purposes, even if that means redistributing them as files.