The "wedge" style rear sights are called dovetail, and you can buy aftermarket replacements (Novak, Champion, MMC) in a vast array of styles and profiles, including adjustable, to replace the stock sights.

Those rear sight "protector wings on the 2nd & 3rd gen pistols look bulky, but I don't think they're that bad... they do keep the rear sight protected and keeps them from tearing up or snagging on holsters.

I have a 2nd gen 559 and put a slide from a 669 to get a two tone look and an ambidextrous safety, which wasn't originally available on my 559. I like the heavier feel of the 559 better than my 3rd gen 4006, and I like the idea of having an older model S&W that's no longer made.

Your single stack M39 would be a much better choice for CCW than the 59/559/5906's... these are definitely a hand full.