Do I still need to clean the tile and grout?
Yes, you still need to clean. Clear Seal does not change the appearance of the tile and grout and you wouldn't even know it was there unless you tested for it like I do before I do any work. Clear Seal keeps dirt and grime from penetrating deep into the grout lines and makes clean up quite a bit easier. In fact, if a quality sealer was applied when the surface was new, then clean up would easily make the grout look brand new without the stains that sometimes can't be removed even by my equipment and methods.
Take a look at the pictures.
This beautiful home is several years old. The owner had the foresight to apply a sealer when it was new. The tile and grout still gets dirty, but my equipment cleaned it all up super fast and it looks brand new.
Clear Seal, at a minimum, is a must!