Hello Rik,
If you are working with extra large models, then it may be impossible to achieve the same quality (level of detail) of the texture, compared to the tiled model, due to the limitation of the texture atlas size.
In such case the possible workaround could be merging the tiles of the most detailed tiled model level to the single mesh - in such approach the merged model will contain the same number of texture atlas pages, as the number of input tiles (so you may want to use larger tile blocks).