I'll chime in with a dissenting opinion. I'll start off assuming that the SFX are not being redrawn. I could rant forever about ungrateful readers and losing days of your life to redraws, but I'll spare you that much at least. A less bitchy/moany perspective is that I think the SFX are part of the manga-ka's art and should remain untouched.
So the next question is how to subtitle the SFX. I've found that a lot of panels quickly become too cluttered and busy when you add the English SFX in lots of fonts and vertical text and stuff. Some people pull it off brilliantly, and sometimes the result is illegible. Personally, I prefer unobtrusive translated text near the original SFX that lets the original SFX convey the "style" and "intent". I like it in the panel, though, and not in the margin like a translator note. I very much dislike when the SFX is transliterated (I think I saw it in a Yen book?). Like all tools, however, I think it really comes down to the skill of the letterer. I've seen good and bad versions of just about everything (except transliteration) XD
The one place where I waffle is with handwritten SFX. Those aren't really art and so could be erased and re-typed, but here is the crux of my dilemma - consistency. To me, it's inconsistent to leave some SFX while erasing others. I worry it will look like I was lazy and left the big SFX but redrew the little easy ones. So for DMG, I've been subtitling them ALL. I'm still not 100% sold on this, so feel free to convince me otherwise