Probably the first time you used the microSD card was directly connected to the Mac using an adapter and you were able to copy music from the Mac to the card. Both Windows and Mac write hidden files that do not affect the DX200 (in some previous firmware some dstore mac files were seen in the DX200 but they are no longer visible). These files are written by the operating system not the formatter. If you are seeing these files you have selected to see hidden files in the Mac. In Sierra and High Sierra is easy to show/hide these files pressing command+shift+. [period]. I should hide them as they are just useful for developers only.
In relation to selecting Artist or Genre, you have "not" mentioned that you scan the card when you introduce it for first time or change its contents. Mango does not know the contents until you scan the card (actually scans the metadata of the music files). Once scanned, Mango has a lists of Artists, Genre, etc. And will reproduce accordingly.
You can also force a scan sliding the screen of Mango to the right (slide a finger from right to left). In the last screen select Rescan Library.
One problem however. Your files must have the correct metadata. That is, if a file does not contain a Genre or Artist tag, the DX200 (or any other player from Fiio, A&K, Denon, Onkyo or Sony) will not know which genre that song belongs to. Therefore you have to display the metadata to ensure that is complete and adapted to your needs. One solution is to use iTunes that lets you review the tags included in the file. However, iTunes does not read DSD files (but can read any format in PCM).
Although one could expect that purchased music files would be properly labelled, that is not the case. I have found that a lot of commercial downloadable music come with little or no metadata. For example, WAV files do not contain metadata (due to the format not the record company) and AIFF format should be preferred. Some have no genre included. Some include an artist that does not correspond to the disc. Therefore, there is a little work to be done before having a proper experience with genre and artists. There are 2 programs for Mac that I normally use: Dapper (
https://itunes.apple.com/es/app/dapper/id903223330?mt=12) for making lists from iTunes and Metadatics (
https://itunes.apple.com/es/app/metadatics/id554883654?mt=12) to correct tags in batch mode (all the files of a disc in one go) of a folder of music files.
Like other DAP, the DX200 is a computer with an operating system (Android) that reproduces high definition music (and mp3 for that matter) and will require time to master it. In my opinion and having listened to other players, it is the best sounding device I have heard. Perhaps, it is not an all tasks device as some of the reports in reproducing Tidal show. But Tidal streams PCM that can be reproduced by any capable Android or iPhone device. The clicking noises were present in the DX200 some time ago. They were due to FLAC/ALAC files changing bit rates from song to song and the DAC Sabre chips adjusting the changing rate. They are no longer present in FLAC/ALAC (that are lossless compressed formats and have variable bit rates for every file) but can be present for Tidal that uses a similar lossless compressed format. A question however, if Mango eliminated the clicking sounds, does Tidal app let them?