Thread hasn't been active for 7 years, but since I was also researching orcs vs goblinoids to try and make them feel distinctive, I'll add my two cents.
In my campaign world, there used to be a large empire that conquered and enslaved almost the entire continent. It collapsed three centuries or so ago and things have been a mess since, but are now steadily stabilizing.
Hobgoblins adapted to the empire by becoming mercenaries for the empire's legions. They still fill that role now, marketing themselves as "ruthless, efficient, no questions asked". They are a common sight in larger towns and they're semi-accepted within civilized lands, because they usually respect the rules. Hobgoblins that aren't inclined to work for others live in fortress-settlements that dominate the surrounding countryside, demanding tributes and taxes. The hobgoblins there live as ancient Spartans and are heavily focused on soldiering. They use serfs to grow their food, goblins to do their dirty work, and sometimes bugbears for heavy lifting or targeted assassinations. The only thing hobgoblins make themselves are their weapons and armor. They prefer tactics where a few of them use flails and guisarmes to trip, after which the rest of the group attacks the downed opponent. With the Pathfinder-artwork in mind, I present them as a sort of goblin/dwarf hybrid: short legs, strong muscled arms, well-equipped, but hairless, big ears, green or grey skin. Other races sometimes refer to hobgoblins as dwarf-goblins, which actual dwarves find super-insulting.
Goblins are pretty much as they are presented in the Bestiary. The reason they survived the empire is simply because they breed faster than they can be eradicated. Seeing their alignment is NE, I try not to present them as overly chaotic, even though it is tempting to do so. I try to emphasize that, once you bully them into submission, they actually make pretty good evil minions that won't try to backstab you first chance they see and individual goblins will actually try to come up with good ideas and evil schemes for their master, to get in their good books. Remember they don't get a penalty on their intelligence scores (none of the goblinoids do!), so they're actually quite smart.
Bugbears are still around because they're naturally solitary and stealthy. They just laid low for a few centuries, and also offered their services to the empire occasionally as assassins or trackers. In appearance I usually present them as orc-sized goblins with furry arms, legs and backs. The main giveaways that they are not orcs are the huge ears, and the furry body. I actually find the difference between orcs and bugbears (other than the sneaky tactics) the hardest to really differentiate between. I think bugbears are probably most interesting in group dynamics with other goblinoids (working for hobgoblins, bullying goblins).
Orcs are like hobgoblins, except chaotic. They band together, they like combat, but there's no chain of command, they don't take orders, etc. In short: they are s+@#ty mercenaries and much more trouble than they're worth. So the empire drove them off the continent. They now fill a role as pirates/vikings in my campaign. They inhabit a chain of barren, mountainous, volcanic islands to the north (think Iceland) where they worship demons, hunt mammoths and whales, herd aurochs and polar swine, and live off the land. Every winter (when nights grow long and they can use their darkvision to their advantage) they get into their longboats and start raiding and plundering all along the northern coasts and rivers. Some raiding parties make disorderly camps, fortified with wooden pikes, to spend the summer on the mainland (players think "orc summer camp" sounds nice until they actually encounter one). Camps are populated with orcs, boars (which they keep as pets, guards and garbage disposal) and sometimes local ogres that they enlisted. Really badass orc chiefs have dire boars as animal companions and mounts. Orcs are feared for their warriors that wield double axes and for their hunters that take down large prey with composite longbows. Their appearance is also like vikings: savage humans, big and burly, with strange haircuts, beards, facial tattoos, in addition to the usual orcish jutting tusks, pig noses, etc.
