2 paths are open at a time, and they change every 4 days.
Spiders and Acid is path 1 and 2.
Spiders and light is path 1 and 3
Acid and light is path 2 and 3
Path 2 and 3 is considered the easy one, since you don't have to deal with the spider minions, so if you are just trying to do one kill for the Completionist cape requirement it would be best to do that.
I'll want to learn how to do the boss properly at some point, but for now my priority is comp, so I guess I should try it now. Is there any difference in setup for the particular open paths?