thanks for answering and giving me the list of shortcuts.
As for the shuffle, I instinctively thought that holding select and dialing the tempo button would change the shuffle, but no. Maybe in a future update.
I know I can load instruments, what I am looking for is saving a specific instrument, but that does not seem to fit the concept of Spark. I guess creating a full banks of f.e. kicks or snares is a way to work around this, this way I have those as kicks/snares as available instruments.
The tap tempo, there I thought Select+Tapping the Stop button might work, but it does not. I actually don't want to change the interface to the Spark one, I do have a SparkLE and seeing a different interface on the screen is just weird.
With the preview, I have my library on a SSD, so that can't be a problem, it seems the delay is built into the software, which makes sense. While browsing through instruments/kits you don't want them to preview right away. However, the current delay is just a bit too long for me. Again, maybe in a future update.
Thanks again for your help!