Best counter vs water

Grass is definitely the only way to go here for the resistances. Although Lanturn does pretty well is a bit underrated.

VW SB Venu may not have enough Atk to win the pure DPS race at potential Suicune raids I assume?

Nobody knows. It will come down to the number of players, this is far more important.

Eggy & Venusaur are the best choice. For Vaporeon raid you need 6 of them. 3 Eggys, 1 Venusaur and 2 joltons are not enough. I failed with timeout and 2% Vape health left. 1 charge move more would have done it. I definitely need a 4th Eggy ES/SoB. And I think, I will turn the fast move of my Venusaur into Vine Whip, cause it loads faster.

You cannot gate C with TM, is legacy move. Only ES, but vs water BS is better.

Victreebel with RL/SoB isn't bad, and it is more tanky since it has higher HP at the same level.
I also am throwing in my Vileplume since I don't have 6 of the others.

Gen 3's ludicolo will double resist water (grass/water) while dishing out STAB SE grass type moves

And although it doesn't deal SE damage, STAB db/outrage Kingdra double resists as well