Trading - where and with whom

My settlement is doing quite well now, I’m thinking it would be good to start trading with others but so far I’ve only encountered one group, the Old Guard, at the refugee centre. How should I look for others? I would particularly like to meet the caravan and trade.

Btw, do NPC factions actually grow or move around the map? Can survivors I encounter alone establish some sort of camps? Right now they barely ever have anything valuable to trade even though I’ve seen them moving around buildings as if scavenging.

If you come across a walled apartment complex base. Sometimes it is a bandit base. If you knock on the gate(with explosives) I know they like that sorta thing. Greet them kindly(with a sniper rifle) and trade some great items(bullet to their head and gather their gear).

Wave bye as you open the gate and drive away in a new mint vehicle they traded you, with a smile.

Cheers(dead pool says KEEL ZEM KEEL ZEM ALL!!!) lol

What about other factions? Where may I find them? Refugee camps?

There are no other factions yet. This makes me sad and I encourage people to cheer meup by contributing new factions.

Are you sure? The game’s wikia mentions factions and I’ve encountered the Old Guard so far. I was mainly wondering where and how I may find the traders.

Might be a mod add on but I’ve found traders hiding under derelict properties

Pretty sure. In an unmodded game, the factions are:
Your Followers - your NPC companions
Old Guard - Two at the Evac Center, a dozen or or so somewhere else but not merchants.
Free Merchants - A lot of people at the Evac Center, including 2 merchants.
Tacoma Commune - An outpost of the Evac Center at the ranch that you can help build up, with 3-4 merchants.
Hells Raiders - Bandits that are always hostile.
Wasteland Scavengers - A catchall faction for everyone else, including two city survivors.

Do bandits actually appear outside of scripted quest events? Like the ones given by the Old Guard dude.

Roadblocks produce bandits, but I think that’s the only other source in vanilla.