UnionFS or MergerFS

Hi, I have a question. I see that you used MergerFS in Rclon to connect the disk. My vision is to create a library that combines cloud storage into a single point of view without the need for recording. It will only serve as a media player. In the case of Rclone via Union, when using several clouds, the loading takes an awfully long time, my question is what is better to use MergerFs or UniunFs to connect multiple cloud storages to one point that will only be for playback.