Yes anti estrogens can effect the gains you will make on a cycle i doubt 10mgs a day of nolvadex will though although 10mg of nolvadex might not have much effect at all with those doses.
Your body grows best with some estrogen present in your system but regardless you still want to use an anti E you dont want gyno.
If you arent worried about bloat i would go with 30mg of nolvadex a day as nolvadex binds to the receptor site that causes breast tissue to develop when there is too much estrogen present, but it doesnt stop estrogen circulating around the rest of the body thus doesnt do much to prevent bloat in my opinion.
If you are worried about bloat i would use 0.5mg of arimidex ED as this stops
test aromatizing to estrogen throughout the body
Bottom line is always use an anti E of some sort