With this perk, will people detect you normally or will it be as if you are sneaking all the time?

Caution if you're running, and you can go as fast as you like in sneak mode without the enemy seeing you to remain undetected.

Here is the wikivault page about it http://fallout.wikia.com/wiki/Silent_Running

Thanks

Not sure if you are asking if getting this perk means not having to crouch to sneak. So to answer that, yes you still have to crouch to sneak with this perk.

I have this perk and I also have 100 in sneak and it ROCKS! I did a previous campaign without Silent Running but still got my sneak up to 100 and the difference is very noticeable. Before even with 100 sneak I still had to move pretty slow to remain undetected. With Silent Running though I can pratically walk right up to most any humun/ghoul enemy and "sneak attack" them from what appears to be about 10 ft away, and that is with them facing me and not in the shadows. I gotta be a bit more careful with monsters like Deathclaws and Cazadores. I still move at full sneak speed, I am just more weary of staying behind them as much as I can and I don't push it, so I get to about what appears to be around 50 ft, well within VATS range for 95% head shot with a sniper rifle.

Also, not sure if this is related to Silent Running or more to having high Sneak but I can fire a lot more on a group of enemies before the caution shows up. However if I shoot once and displace, even just what appears to be 10 ft from my previous position, I can remain undetected til the cows come home.

One of my favorite perks, since I get impatient at having to move sooooo slooooowly.

Totally this.
Oh sure you can do a lot of general, casual sneaking with no silent running and while run-crouching but if you want to be really sneaky...the walk-sneaking drives me insane. heh