Competitive team help for b/w2

I'm need help looking for pokemon to help make my team stronger or help improve my team.
Pokemon with a * means pokemon that i plan to keep
im not sure with what the evs were for the pokemon but i'll list the most accurate
Cresselia
ability: levitate
Hasty nature
hold item: leftovers
evs: 252 sp def., and i split it between def and hp unsure of the amount
lvl 71
hp: 284
atk: 120
defense: 173
sp atk: 131
sp. def: 238
speed: 178
might changes moves to make her a dual screen
moves: light screen, toxic, moonlight, psychic

*Togekiss
ability: serene grace
evs: 252 speed, 252 sp atk, 4 hp
hold item: quick claw
Relaxed nature
lvl 89
hp: 293
atk: 106
def: 228
sp atk: 248
sp def: 243
speed: 181

moves: roost, air slash, thunder wave, aura sphere

*Heatran
ability: Flash Fire
started adding the evs to his SpD gna make it 252, 252 hp, and 8 speed
hold item:???
Calm nature
lvl 68
hp: 219
atk:132
def: 162
sp atk:196
sp. def: 194
spd: 119

moves: protect- might switch it, lava plume, stealth rock, toxic

Latias/latios- dont know which to use yet
Ability- levitate
hold items: ??? prolly life orb
1st stat or nature is latias's second stat is latios's
evs: latias is 252 spD and speed, 8 hp
Latioas 252 spA and speed, 8 hp
Jolly/Gentle natures
lvls 81/76
hp: 245/222
atk: 139/157
Defense: 150/121
sp atk: 195/258
sp def: 248/ 221
speed: 239/229

Latias moves: recover, calm mind, psychic, dragon pulse
Latios moves: Surf, recover, psychic, calm mind

Thundurus-T
Bold nature
lvl 40
hold item:???
Volt Absorb ability
no evs
hp:124
atk: 90
def: 79
sp atk: 141
sp def: 71
speed: 109

moves: thunderbolt, volt switch, focus blast, and agility

I was also using a volcarona here's his stats
lvl 74
hold item: ???
Ability: flame body
Adamant nature
evs: 252 speed and spA i think 8 spD
hp: 229
atk:104
def: 101
sp atk: 219
sp. def: 189
speed: 202

moves: bug buzz, quiver dance, flamethrower, fly- gotta get around the map lol

Pokemon preferences for my team is accepted and i know my team is in disarray lol. But anything is helpful. Looking for a competitive team so I can make it to the top.

You're going to have to do some re-breeding/resetting with some of your Pokémon, I'm afraid.

Hasty wastes away Cresselia's incredibly high Defense. It's meant to be a support 'mon rather than an offensive one:
-Moonlight
-Psychic
-Hidden Power (Fighting)/Ice Beam
-Thunder Wave/Toxic
Nature: Bold
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers

Togekiss should use a Bold nature. Luck-based items like Quick Claw are frowned down upon competitively, as they need, well, luck, not skill, to work:
-Thunder Wave
-Air Slash
-Roost
-Aura Sphere/Nasty Plot
Nature: Calm
EVs: 252 HP/56 Def/200 SDef
Item: Leftovers
Ability: Serene Grace

Calm nature is good for Heatran. The EV spread should be 248 HP/252 SDef/8 Spe:
-Lava Plume
-Stealth Rock/Roar
-Will-o-Wisp/Toxic
-Protect
Nature: Calm
EVs: 248 HP/252 SDef/8 Spe
Item: Leftovers

Which Lati you intend to use depends if you want to go offensive or defensive with it:

Latias:
-Calm Mind
-Dragon Pulse
-Substitute/Hidden Power (Fire)/Psyshock
-Recover
Nature: Timid
EVs: 252 HP/4 SAtk/252 Spe
Item: Leftovers

or
-Draco Meteor
-Psyshock
-Surf/Hidden Power (Fire)
-Recover
Nature: Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Life Orb

or
-Reflect
-Light Screen
-Healing Wish
-Draco Meteor
Nature: Timid
EVs: 252 HP/4 SAtk/252 Spe
Item: Light Clay

Latios:
-Draco Meteor
-Psyshock/Thunderbolt
-Surf
-Trick/Hidden Power (Fire)
Nature: Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Choice Specs/Choice Scarf

or
-Draco Meteor
-Psyshock/Thunderbolt
-Surf/Hidden Power (Fire)
-Recover
Nature: Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Life Orb

or
-Calm Mind
-Dragon Pulse
-Surf
-Recover/Psyshock
Nature: Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Leftovers/Life Orb

or
-Reflect
-Light Screen
-Memento
-Dragon Pulse
Nature: Timid
EVs: 252 HP/4 SAtk/252 Spe
Item: Light Clay

A Bold nature is wasted on something like Thundurus-T; it's meant to be an offensive 'mon. If you can get someone to trade you a Timid Thundurus from White, you can use the Reveal Glass to change it to its Therian forme:
-Agility
-Thunderbolt
-Hidden Power (Ice)
-Focus Blast/Grass Knot
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Life Orb

or
-Thunderbolt
-Volt Switch
-Hidden Power (Ice)
-Grass Knot/Focus Blast
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Expert Belt

or
-Thunderbolt
-Volt Switch
-Hidden Power (Ice)
-Focus Blast
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Choice Scarf

or
-Nasty Plot
-Thunderbolt
-Hidden Power (Ice)
-Focus Blast/Substitute
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Life Orb/Leftovers

Volcarona's Quiver Dance sets can be all-out offensive or even defensive. Adamant also wastes away its high Special Attack. You can always use something like Pidove or Ducklett as your Fly slave:
-Quiver Dance
-Fiery Dance
-Bug Buzz
-Roost
Nature: Bold
EVs: 240 HP/216 Def/52 Spe
Item: Leftovers

or
-Quiver Dance
-Fiery Dance/Fire Blast
-Bug Buzz
-Rest
Nature: Modest
EVs: 160 HP/252 SAtk/96 Spe
Item: Chesto Berry

or
-Substitute
-Quiver Dance
-Bug Buzz
-Fire Blast/Fiery Dance
Nature: Timid
EVs: 4 Def/252 SAtk/252 Spe
Item: Leftovers

or
-Quiver Dance
-Bug Buzz
-Fire Blast/Fiery Dance
-Hidden Power (Rock/Ground)/Psychic
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb

iight thank you guess i am going to have to do some major trading but the reason is used quick claw is because you can not use two of the same items I believe when competing. So I got a lot of work to do to make my team better but do you recommend switching out a pokemon because I was using both of the eon twins because it was cool.

You can have more of the same item, I believe people don't usually put the Item Clause in effect. There are also better items to choose from than Quick Claw. [will edit this post when I'm on computer]

cuz when you do battles over wifi they have that clause in effect and how far do you think this team will go?

Ok so I have took what yall told me and remodeled the team. I will use heatran and togekiss with your preferences
So here is the new team
Heatran same nature
Togekiss your preference
I have a lvl 68 cresselia with a relaxed personality
hp 249
def 195
sp atk 124
sp def 181
speed 140
ability: levitate

Moves: trick room, psychic, light screen, safeguard not sure on this move

larvitar atm gna make it a tyranitar with sandstream ability
adamant nature
moves: stone edge, dark pulse, earthquake, pursuit
ability: sand stream

mudkip= swampert
adamant nature as well
ability: torrent
moves: waterfall, earthquake, ice punch, toxic

So as you can see I am making a team that will floursih in the sand stream and with trick room makes swampert and tyranitar flourish at the speed game.
But as you can see I am missing that 6th man
I am considering garchomp but I believe that he is banned from competitions since he is OU or dragonite, blissey, or what do you recommend?