ReaSnow S1 does support 1000hz, there is no doubt about that.
here are some more explanations for choosing a DPI:
1. DPI
based on the data we got from many mice,
with a high DPI(10000DPI or above),
some mouse will easily detect the tiny shaking of your hands or even the desk,
uneven mousepads will also bring trouble for your aiming.
you will not like that for fps games.
5000dpi~8000dpi can give enough turning speed and much better and stabler aiming,
which is critical for gamers.
2. USB report rate
yes, as you can see from many USB analyzers or mouse testers,
the USB report rate can't be kept as 1000HZ even if it's set to 1000hz.
so why shall we use the report rate which can be kept by the mouse itself,
stability and reliability during the intense competition will be a great advantage for most gamers.
3. ReaSnow S1's engine is trained and tested with 5000DPI/500HZ.
we always use 5000dpi during all these procedures,
so 5000dpi will be a good choice for the defaults settings in ReaSnow S1