Half a level finer than the reference, with a shorter style zoom lift. Meant for a phone: visibly sharper than the reference at roughly twice its tile count.
A full level finer than the reference (TileLODFactor 0.5, the historical default), about 4x its tile count. Meant for a desktop or a web page on a real GPU.
The reference density: TileLODFactor 1, the tangram/mapbox/maplibre rule - a tile is refined while it covers more than a 2x2 block of nominal tiles. Fewest tiles.