Preparing for Palkia

Charge beam is the better move to have on gardevoir for this, according to pokebattler. Though gardevoir seems to only do well against Draco meteor; hydropump and fireblasts are for the dragons

Wiggles and clefable, not good, fairy is a weak type offensively in general, even gardevoir struggles to stand out. the dragonite, while not the best, is certainly much better. Even against Draco meteor sets, while the take significantly more losses, the dragons still deal out a lot more damage a lot faster.

The DT/OR Gyarados is good, i'd reomend TM'ing the Hu dragonite to OR, the DT/DM dragonite is fine in moveset, at higher levels it will do great, The Rayquaza, it needs little explainations it is rayquaza and its fantastic with double dragon.

I wouldn't stress too much about having counters for draco meteor, its not the hardest move to dodge, though it will likely one shot your dragons, though if you have a larger group size, relobbying may not be an issue so long as you all are bringing good counters,
I wouldn't evolve a togetic, the sinnoh stones should be saved till we hear more about mamoswine in my oppinion, and the kirlia i'd say evolve depending on your situation. If you have a group you regularly raid with and have good counters and know what you're doing, it really only is good against draco meteor, which you can practice the timing on dodging with by battling gyms (some friends and i did this, 4 mystic, 4 valor and 4 instinct take gyms, put pokemon in them with movesets as the raid boss to try to get the dodge timing down better) to avoid dragons getting One shot. if you arent able to dodge DM well enough consistently, i'd say evolve the kirlia

As a side note, palkia is a fantastic self coutner, ie it works great as a coutner to itself, much like rayquaza, depending on moveset palkia is actually the faster counter, due to double resistance and better bulk, so even if you lack some dragonite/rayquaza, you will still have access to one of the top 3 general counters

You don't need separate teams for DM/non-DM Palkia. Dragons are the best counters against all movesets, they just die faster against DM. Unless you really want to avoid rejoining (for example if you want to walk away from the gym during the raid) or you somehow manage to be low on revives, there's no reason to change your team for DM.

DP Dragonite is fine, still top 5 level TTW with that moveset. Clefable and Wigglytuff are unfortunately trash. Togekiss, Gardevoir, Granbull are the only fairies worth using, they're actually pretty decent.

Including the DP Dnite, you have a team of 5, it's really up to your personal preference which one you'll make for the sixth. You can TM the Hu Dnite, power up the Rayquaza, power up the DM Dragonite, evolve and power up another Gardevoir or the Togekiss or lastly, power up the Gyarados. All of these are acceptable options. Rayquaza is the best, Togekiss without HP:Dragon is the worst, Gyarados is the second worst.

Or if you don't want to spend any resources, use your best Mewtwo with either Shadow Ball or Thunderbolt. Still better than Clefable or Wigglytuff.