For Passimian definitely Jolly. If you expect to get Defiant boosts and your base Speed is 80, you should really prioritize Speed.
Jolly is also much better in combination with a Choice Scarf because Adamant fails to outspeed stuff like Aerodactyl, Jolteon, Crobat or Mega Gengar.
Symbiosis on Oranguru is completely niche and I don't think that it will see much play.
One thing you could theoretically do with a Symbiosis Oranguru is allow a partner Xerneas to use Geomancy twice in one turn.
Xerneas would do the classic Power Herb Geomancy play after which Oranguru's ability would activate and pass another Power Herb to Xerneas.
Later during that same turn Oranguru could use Instruct on the partner Xerneas and make it use Power Herb Geomancy a second time, which would give you a +4+4+4 Xerneas in one turn. The following turn Oranguru could use Psych Up and things would get out of hand fast.
I don't think that a Quiet nature would be very helpful or necessary in a scenario like this and you might even want to consider Timid here to increase your chances of getting to Instruct unhindered.
While all of this may sound tempting, it isn't legal under VGC rules where item clause applies. You could maybe do this in Smogon Doubles Ubers or something, but who seriously plays that on cart?
I don't see any other uses for Symbiosis so I don't think that the ability matters much when choosing the nature for a HA Oranguru.