Pokemon Total = 27
Trainer/Supporter Total = 23
Energy total = 11
This is a deck built by one of the best pokemon players I know, so there's very little, if anything, that I can suggest as changes. So most of this review will be on the strategy. Ideally, you'll start with a mew in the active position so you can use 'see off' to put a muk in the lost zone. Mew is able to use the attacks of any pokemon in the lost zone as its own, but for the same energy cost. Muk's first attack allows you to drag a pokemon off of the bench and once it's in the active position, it's poisoned and confused. With vileplume on the bench, your opponent has to manually retreat out of the status conditions rather than use switch, making it more difficult. Ideally you'd target a heavy retreater so that they're forced to stay active longer and take the damage from poison.
There's two other attackers in the deck that mew can utilize - jumpluff and aipom. If you can bring up a heavy retreater with no energy, you can use aipom to move any energy they attach to the bench. This stalling may be enough to allow you to finish get setting up. Jumpluff is the heavy attacker, hitting for more when there's more pokemon on the field and giving mew an option for putting out damage.
The secondary attacker of the deck is yanmega prime. Once you have a heavy retreater in the active position, taking the poison, yanmega starts spreading damage by sniping the bench. The deck can take KO's this way, or it can just keep spreading to KO key attackers.
Jirachi is the final attacker if the opponents deck contains evolutions. Jirachi can de-evolve multiple pokemon in a turn, and with all the damage put on by yanmega sniping, this should ensure multiple knockouts. These late game KO's ensure that you'll have access to your twins engine throughout most of the game, helping you get set up.
Aipom is probably the only pokemon in this deck that I think can be easily dropped. The damage from poison will ensure that eventually that active pokemon is KO'd meaning that they won't be trapped in that active position forever. In other decks like chandelure vileplume, the aipom works much better because once a pokemon with two or more retreat cost is active, unless they play DCE, they can't get out. So in this deck, aipom is just a staller and it would be more beneficial to use that time spreading damage with yanmega or using mew to bring up different pokemon from the bench to take damage while you get set up.
I don't see any reason to change a thing.
When I've played this deck, the biggest thing that I struggled with was the lack of recovery. I often found that something was prized or could have won the game if I just had one more yanmega or one more mew. For that reason I'd add a flower shop lady. I'm worried that by reducing your collector to 3, you reduce your chances of being able to get a double oddish out. I'd say 3 collector is only a good idea when there's a pichu. Which means we still have to find room for it. I'd probably feel safest by dropping a sage since it's not something that the deck really relies on (unlike the judge and copycat for hand-matching).
This deck has always been a great deck, but always seems to flop at tournaments. It can struggle against the clock in tournament since there's many times where it won't take prizes until later in the game. Since there's pokemon that are run in small numbers, this makes it more probable that they're going to be prized. We might see an increase of this type of deck if mewtwo ex's start to get really popular since mew can use jumpluff's attack to KO a mewtwo in one hit!