that would be Group 2!
I agree, and echo, with tglassy on all points.
also, I took into account difficult terrain for my movement ( i contemplated asking you but i didn't want to interrupt immersion, and I felt (read: meta) that it should be ...swamp= difficult), as that is a factor to make a single BBEG encounter challenging for a party. It's part of our toolkit as DMs and we must use them (< I know I learn this lesson all to often lol)
I am on my 4th campaign for 5e as DM since 2014, and I've learned that single mob single attack gets eaten alive, even if my PCs dont work cohesively they still have upper hand with numbers, so i often ramp up the CR on single mob encounters ( if they are to be challenging...nto all encounters need ot be challenging , nor do they need to be melee...but that is another discussion for the 6 or 7 per long rest...). Sometimes its just adding terrain and view obstructions, often i variant spell casting into the creature if able. That being said, I still incorporate the easy and medium encounters into the mix. It's fun when the suspect some random non threatening creature is an illusion or something more to it.
Flip side, to many enemies becomes bulky, especially at levels 5+ since your melees are now into the 2 attacks per round. 20+ kobolds are difficult maintain (I do keep enemies on a single initiative, but i will give each type of enemy its own, so that helps when rolling 20+ attacks ), but certainly challenging when utilized as per Tucker's scenario. I imagine that miniature management can be trickier in PbP?
And on the aside, you know we all thought it was a shambling mound, that could have been an interesting scenario as well if we had befriended it, though looking at their ecology I am not sure they are befriend-able
