Word for "one who configures"
Solution 1:
In practice the normal term would be installer, but configurer and configurator could be used. I think most people would understand these words, even though they don't normally use them.
Solution 2:
Configurer is the appropriate form, even if the double |ərər| at the end of the word seems strange. Consider other nominalisations that end in |ər| (like 'conjure' -> 'conjurer').
Solution 3:
I thought of one possibility: tuner