I mean in a perfect world, If I had time to get my pikmin into the order I want, such as blue, purple, red, then I would look for a grab to follow up with up smash then fair for maximum damage. But, do you don't always get that, more like rarely. My myself, I kind of dislike having unflowered white pikmin, so I always just chuck them at the opponent, not really caring what happens with them. I really dislike grabbing with purple pikmin, so I usually avoid trying to grab with purple pikmin in front. But, these are definitely habits that the opponent can pick up on if he/she is familiar with olimar as a character. If I have like a red, blue, yellow, then I just do whatever is good for the situation. It is very difficult to always get that dair or uair with your red pikmin, or your d-throw combo starter with your blue. For killing, I only try to grab for kill with blue pikmin, but a lot of my kills come from up smash or fair/bair with any color other than white.
One thing I really dislike having happen, is losing your stock before your opponent when they are close to death, then only pulling like yellow and white pikmin mostly. It makes it a lot tougher to kill, so I just try to throw them away quickly to pull new ones. My overall goal is to have a combination of red, blue, and purple pikmin because they seem to be the best in most situations.