You actually need stealth more than pickpocket. You don't even need a high sleight of hand for that due to how much of that is in the form of money and the game undervalues money for pickpocketing difficulty.

It's useful only for a few thousand gold over the course of all the pickpocketing-nothing really special otherwise (might be useful early on, but doing a few mid-game quests quickly trivializes those returns). TL DR - in base game, it's not worth the skill investment. I had a post a long time ago where I judiciously pick-pocketed every single non-hostile NPC. But Loaded Pockets is what makes it worth it. Some NPC's have fixed loot, so you could go for that. Without the perk, it's just for the money I think. It's rare, but If you get the loaded pockets perk then yes. So it's easier to pickpocket moving targets - if you can predict theor movement. Running victims have a much smaller hearing circle than victims that stand still. They will run towards the source of noice you can sneak up behind them. This doesn't work for most neutral npcs like merchants. You can use spells on the ground to lure hostile npcs and guarding npcs (shield + eye symbol over their heads) towards a place and sneak up behind them. I think if bystanders detect you you are also 'detected' and can't pickpocket.

Neutral victims don't care if the circle becomes red - as long as it's not fully red. Hostile victims will already start looking for you and move towards the noise you make as soon as the cicle turns from yellow to red - so I guess pickpocketing them would be a real challenge (never tried I have to say). If there's even a fraction of the circle not red you are good to go. You can pickpocket as long as the circle isn't completely red. Generally speaking: if the circle is fully red you are screwed. You want to take the shortest route to the victim and that's often impossible if the party is trampling on each other's feet. Way easier to mange if you are only steering one party member during the attempt. Also the pathfinding is difficult with all party members. Well technically you can use the whole party to sneak up onto the victim, but you'll never know which party member will attempt to pickpocket then (presumably the dude with the highest pickpocket skill) - maybe it's that one party member who already screwed the stealth.

Divinity 2 pickpocket guide