I personally use bing when I'm not subbed. I think I tried the "free" one at some point and it was a lot worse imo. Things may have changed since then though. Also as
w1ndow said, there's a setting to change font size. When I use mtool's translation, I usually have to set it down to somewhere between -12 and -15. Though you might need it fullscreened to see the text at that point.
As for English/Japanese setting, I leave it at English. Mtool doesn't catch stuff from the Japanese setting. Mind you, not
every line gets pulled for translation... plenty of option choices (like simple yes/no) and a few map/warp location names remain.