Looking for VGC series 10 suggestions!

I'm relatively new to competitive Pokemon, and the team I have so far focuses on speed control. Would greatly appreciate any general feedback! I'm not too good with EV spreads (I just took some off of Pikalytics) and am also trying to decide on a good 6th Pokemon to use

Kyogre @Mystic Water
Ability: Drizzle
Timid
4/0/0/252/0/252
Water Spout
Origin Pulse
Ice Beam
Thunder

Tornadus @Focus Sash
Ability: Prankster
Timid
4/0/0/252/0/252
Taunt
Hurricane
Tailwind
Protect

Stakataka @Grassy Seed
Ability: Beast Boost
Brave
0/252/252/0/4/0
Gyro Ball
Rock Slide
Body Press
Wide Guard
**Debating on whether I should replace one of these with Trick Room instead?

Cresselia @Mental Herb
Ability: Levitate
Calm
236/0/108/4/76/84
Ally Switch
Helping Hand
Ice Beam
Trick Room

Rillaboom @Assault Vest
Ability: Grassy Surge
Adamant
252/252/0/0/4/0
Fake Out
U-turn
Knockoff
Grassy Glide