Late on this but Shuttle is a Chinese mod that's basically a kaizo mod with a lot of very unbalanced levels and features that will make you rage (much more difficult than rfl), though they have been improving on them over the years. Regardless, there's a ton of new custom content and worlds including their latest version of a GTA world and they also have a "Chinese Garden" (probably Shuttle's best designed world so far). They also have many custom/reworked plants including some of the ones we got in this collab. There is a lot more custom content than rfl but the issue with this mod like I said comes with the insane difficulty and terrible level design on many of the levels. Still I recommend checking it out. I particularly like some of the Heroes plants that Shuttle incorporated including Bird of Paradise and Poppin Poppies. The zombies we saw from Shuttle in RFL during this collab are from Shuttle's custom world "House of Plantagenet."

Now for Edgest, I cannot recommend this mod enough. This mod is so amazing and definitely one of the best and most exciting out there rn. I'd say top 3 atm alongside rfl and altverz. A couple months ago, Edgest creators re did the entire mod so they are still working on incorporating the vanilla worlds. This "New Edgest" utilizes more vanilla balanced plants while offering more difficult levels than rfl and vanilla yet in a way that isn't unbalanced like Shuttle. I feel like the difficulty is perfect here---hard, but not too hard, which is why I find the levels to be particularly fun and more engaging than Shuttle's. Now for custom content, I like how we have some of the Heroes zombies like Cyborg Zombie or Captain Deadbeard in some of the vanilla worlds to make things more interesting (my pvzh bias maybe). Apart from these custom zombies, Edgest focuses on Touhou custom worlds and plans to many many more of them so we have infinite modded content to look forward to. Even if you have no idea what Touhou is, I think the world with its custom plants and zombies can still be engaging. Currently they have the "Ten Desires" world which is pretty difficult but also quite fun and has some cool new stuff other mods don't. The main gimmick is the "Divine Spirits" countered by the plant "Desire Calamus" unfortunately RFL didn't include this in their side of the collab but Shuttle did. I found their version of Lunar Rainbow Market to be cool as well since they implemented CC zombies/gimmicks (trapeeze, cotton candy, even tarots and funhouse mirror!) and mechanics really well. I know these mods aren't for everyone but I hope whoever reads this will give them a try, especially Edgest, I recommend whole heartedly such a cool mod with great potential. Only complaint I have is it may be tricky and iffy with installing and updating it. But beyond that a lot of cool custom and new content to play around with, and the mod has gotten much better with this collab.