The Dragon team looks pretty good, I think having a megaless Dragon team is fine nowadays because of Dragon's mega evolution options being generally lackluster. I'd definitely do enough speed EVs on Dragalge to outspeed Celesteela since you're Thunderbolt, and it allows you to chip it down more. It also helps against things like Swampert and Clefable which is definitely worth. Also do Dragon Fang over Black Sludge, helps against stuff like Toxapex and Mega Sableye which is generally more useful here. Make these changes and I'll add it.
On the other changes, I don't think the Special Attack EVs are necessary on Celebi seeing as you keep Stealth Rock up against Water because of Rotom-W being the main Defog user and you have a lot of other things like Metagross's priority, Mega Slowbro, and Alakazam as backup vs Mega Sharpedo. I'll add the Sludge Bomb Toxapex though, definitely very important in Swords Dance Tapu Bulu meta.
These are all pretty good pending some minor changes. On the Flying, Z-Stone Edge seems like the better option over Z-Fly seeing as it lets you hit things like Rotom-W and Celesteela, while still being very threatening. On Water, I'd say Jolly Mega Sharpedo is good here for sure, you want to outspeed offensive Deoxys-S since that essentially smacks this entire team with a Nasty Plot under its belt, if it happens to set up on something else. Outspeeding +1 base 100s like Victini and Jirachi is also good. The Grass one is good. I'll add these pending the changes.
Looks like a decent team, but I think Chaitanya's and the current sample works fine for Grass. Rejected.
I'm not looking for anything in particular this time, as the generation is ending and I think what we have for samples is fine right now. Thanks to everyone that's contributed to this so far!