How much flavor from prior brews are imparted onto the yeast? Should I only reuse yeast to make similar beers or does the washed yeast not retain much beer flavor?
No flavor is imparted by the yeast itself if you decant off the beer over the yeast. However you should never use a yeast from a higher gravity brew on a lower gravity beer as the yeast have been stressed and will not perform well in the new brew.