This is one of those agree to disagree moments. The changes to the Smiling one are so extreme that it arguably changed it's combat role entirely, from a Rogue-ish Controller to a Ranged Skirmisher. Is it better at mobility? Definitely. Is it better at killing? About even at best. Is it better at controlling? No way.
Corpse Flower (MToF)
An additional way to make your enemies keep harassing your players long after they are dead and buried, the Corpse Flower is what happens when you combine necromantic energies with the power of plants. An intersection of opposite themes that seems to keep happening in 5e, especially in the M:TG crossover space, though the concept is much older than any of our games.
To make a Corpse Flower, simply put the remains of a necromancer or powerful undead in the ground, and wait for a plant to grow. After it reaches maturity in a few weeks, it will uproot itself and start scouring the area for dead humanoid bodies to consume. If it finds any living humanoid bodies in the meantime, it will make those bodies dead and eat them too. It really is that simple. Given the propensity for dead bodies to attract monsters and other undead creatures, it’s a wonder why more D&D communities don’t practice cremation.
As for why your players would want to pluck this flower, there are a few options. The PCs could simply be cleaning up their mess from that time they killed the necromancer and didn’t dispose of the body properly. Alternatively, the Flower is keen on graverobbing, which could spur the PCs to reclaim some lost weapon or quell a ghost by exterminating the weed. Or maybe the PCs are purposely farming one to harvest for ingredients.
This macabre bouquet comes pre-loaded with 1d6+3 corpses, which may be used to either heal the flower or make a zombie as a bonus action. The Corpse Flower should use one of these bonus actions in combat every round, and figuring out which one to use is kind of tricky. On the one hand, making a zombie provides far more defensive utility and helps with the action economy on the side of the Plant. On the other hand, the Flower is a CR 8 monster, and getting even one more round of action out of them is far deadlier than what a zombie can expect to do. As a general guideline, I would recommend using the first two turns to get a new zombie, and every subsequent turn to heal. If somehow the Flower is back up at full HPs, then make a new zombie until the enemy is dealt with. It is also worth noting that the Zombies animated by this power stink just as bad as the plant that made them, allowing for more area control and potential action denial. Unfortunately for the Flower, once you save against this stick from any source, you are immune to it for 24 hours. Making it impossible to stack multiple auras of stench.
The Corpse Flower has two actions in combat, its 3 tentacle Multiattack, and a power that lets them stuff a corpse into their roots for later eating. This decision is much easier to make, Multiattack makes more corpses, so it should nearly always be attacking, unless it is near death, at which point it’s trying to pop corpses like healing potions as it makes an escape. The Flower also has a climb speed, which may be harder to tactically employ in a graveyard, but it could come in handy if they are inside a crypt.
In the changeover, the Corpse Flower’s Tentacle attack was made more deadly, it deals less maximum damage, but no longer requires a saving throw in addition to their attack roll. Creatures like this make me wonder how they are going to change the Zombie, if at all.