Tips for a quick recruitment from barb camps

Possibly everybody already knows this, but I haven't seen it posted here.

In Civ6:GS with Barbarian Clans enabled, not only you can buy a unit from any barbarian camp (even if you don't have direct visibility of it!), but also:

• the unit will be cheaper than buying it with gold in your city (currently an option to buy Man-at-Arms at 640 in city, or 382 via clan);

• it will spawn near the closest city to camp, making you able to recruit defenders very fast;

• you can get units you haven't discovered yet yourself; I just got Pike and Shot, when I don't even have Stirrups yet.

• you can get unique units such as highlanders etc. if it's the clan's specialty;

• the type of unit will match the type of clan. ie. a clan that spawns naval units will have galleys for hire, land camps will have melee units for hire;

• units are individual per camp, so I have Man-at-arms in one camp, while Pike-and-Shot in another (and no civ has got Metal Casting already afaik). Possibly the later spawning camps give newer era units?