Hi Jugge,
Not sure who is selling the song styles on PSRstyles but I can tell you that when PSRTutorials was up and running I, like a number of others, help support the site by purchasing various packs from Joe. I can say that the one I have contains 12,000 files and is very mixed. The 'songs' are named for easy recognition and come in a variety of folders for different instruments.
eg: S700/S900/S550/S910/S970/S975/SX600/PSR3000/Tyros3/CVP509/CVP809/ etc.
The format is split between SFF1 and SFF2
The main issue is the fact that these were produced for a number of early instruments plus conversions by PSR members. As such, many will not reproduce well on modern keyboards as they cannot take advantage of the recent developments in such keyboards.
Whilst I found a number of files interesting and could use them at a very basic level, none could compete with the files that came pre-loaded on my G2.
Many music stores load a substantial amount of additional files as part of their marketing strategy and it is those files I use primarily.
One guy that has been incredibly generous in sharing is Emanuel Meier and a link to his site is below. From memory I beleive there are approximately 2500 song registrations. Easily converted in the G2 as it can convert the T5 musicfinder files
https://tyros5.ch/tyros5_musicfindertipp.htm
(Emanuel, if you read this post, thank you so much for sharing your Tyros MFD, greatly appreciated and I hope you don't mind me providing the link?}
Apologies for the length of the post, but hope this helps.
yogi62