Generally, mosaic bricks are pasted with 70-120 mesh sand because they are thin. If it is vitrified tiles, it is usually recommended to use graded sand, like 40-70, and 70-120 mesh sand. If the proportion of cement and sand is correct, the strength can reach the standard. As for other requirements, it depends on the additives you add.
Since the construction conditions at the site are too complicated, it is generally impossible to apply thin films, so it is better to use coarser sand. The prerequisite is that the sand must be clean. Sometime we did everything, but problems still occur, either a problem of the purity of the additives, or the issue of mud in the sand. If the customer adds additional cement, the impact will not be significant if not much usage. If too much is added, there is a possibility of cracking.