Is Pikmin 2 as soulful as the first game? Pikmin first person reports after each day are great. How do I get good at it...

Sounds really good. The time limit sucks because I suck. But overall I think it makes the game better. At least when talking about Pikmin 1

Yeah, the time limit can be annoying when you first get into the series. I think the more experienced you get with the mechanics the more naturally faster you can work through a day.
The time limit definitely fits 1 well. I think it's good they didn't do it for 2 though. The way 2 is designed doesn't really lend well to a set limit like 1

Nah, Pikmin 2 fixes the AI. Pikmin are unresponsive little shits in 1

You still help them though, each population is down to like 5 individuals before you come back and raise them up again.

Yeah. I feel like previously knowing the map is the only way to get 30 parts in 30 days in 1

Pikmin 2 has the Piklopedia. Every enenye you defeat and treasure you collect gets an entry with an in-character description. Its extra nice because enemies get little interactive scenes where you can watch them scurry around a habitat and throw fake pikmin (carrots) at them which they will eat. The treasures are all real-world things like batteries, forks, jar lids, and toys that Olimar doesnt recognize and makes up his own theory of their use.

Damn, that probably makes the game so much better...

When I get the bad ending in Pikmin 1, should I replay to try a better ending or can I just watch them and move on to Pikmin 2?
I mean, does the gameplay change in any way or the only difference will be the ending cutscene?

Does new play control fix that?

no way
I made it in like 23 days my first blind play through

Yes.
Also they don't use pathfinding to follow until Pikmin 3.
In 1 and 2 you can't walk too far ahead of them or they may get stuck on a wall somehwere.