possible with even higher scanrate than default?

you might try with

Settings.WaitScanRate = a-value-greater-than-3

but with the current implementation, only in very specific situations (small region, an image found vera fast) you will get more searches per second than 3.

If you want to know, what your environments performance is, try this:

reg = some-small-region # (max 300x300)
img = "some image inside that region.png"

print reg.find(img).getScore() # this should be 1.0

s = time.time()

for i in range(100):
   reg.exists(img, 0) # this makes one search only

print (time.time()-s)/100 # this is the time needed for one optimal search

So if this is below 0.3, you might try to increase the scanrate.