I've stolen a crap ton of stuff from virtually every domicile and structure in Diamond City. Agility 5, sneak is now 4 but I was stealing a lot when it was about 3, maybe even 2. I literally stole every last piece of junk in the Mayor's office, pickpocketed him his secretary and the guard! First perk I took was Sneak, and I took Sneak 2 _as soon as I could, and same with 3 and 4. I also didn't expect to be very successful until I had at least 2 and ideally 3. Now that I have 4, if anything stealth feels easy. I can literally sneak up on sleeping Deathclaws with Sneak 4 Agility about 5 _AND_ while wearing Power Armor! 
There is a gigantic line of text in the upper middle of the screen that tells if you are hidden or not, and a whole section in the Help in game that describes what the brackets mean (the move in and out).
You could easily play this game and never shoot anyone. You might have to get others to shoot FOR you, else blow them up or otherwise get them out of the way through violence . . . actually though, now that I think about it, you might even be able to get past a large fraction of enemies using the various Charisma perks (the one that allows you to Intimidate, etc.).
At Sneak 5 and high Agility and with the right gear, you might even be able to infiltrate deep into enemy strongholds, slipping past dozens of guards, retrieve items, kill bosses, release hostages, etc. (although the latter would obviously be difficult to sneak your way back out without a fight).
The idea that you can "only" play the game one way (run and gun) is absurd.
It is FUN to play it that way, and it is the most obvious way, but as far as I can tell, a hacker, sneaker, smooth-talker type playthrough should be very possible; at least as possible as it was in NV or FO3, and probably moreso than in FO2.