As you mentioned, WFs are a little hard to critique because half your game was dsmashes. I imagine you picked it up from playing less competant opponents beforehand, dsmash can be a decent trip-up move in doubles that is more likely to connect and less likely to get hardly punished because of the inherent chaos of doubles. Otherwise it looked pretty good. Your opponents seemed inexperienced against pikachu (for example, they would jump immediately on recovery every time, making jump off nair/dair pretty guaranteed), but you punished them for it and if it's working there's little reason to change things up. You had mostly good edgeguards, which is quite valueable in teams. There were a few times where you and your partner would trip eachother up in edgeguards, so I suppose that's something to work on. Your neutral game was fine, I didn't see many bad habits (except for the admitted abundant dsmashes, which you cleaned up throughout the sets), and it didn't really need anything extra against that team. I saw a number of things that they could punish (like your reliance on uairing from the ledge to get back to the stage), but it kept working on them so it's hard for me to say "that's wrong" when you had no reason in those matches to do differently. You did seem to panic a little under your shield, as you would often get hit out of it or not respond with a good oos option. You did do a good job of not getting stuck in your shield though, so that didn't come up often.
The main thing that did bother me was your team's playstyle. Throughout 6 sets there were very few times where you and your teammate were interacting. That's fine, as you weren't particularly having issues fighting either of them 1v1, and your partner wasn't particularly having issues fighting either of them 1v1, but I think you two would benefit from more team-play. The strategy seemed to be to not step on eachother's toes, each take an opponent to one side of the stage, and just win that way. Not every team will let you do that, and I guess more to my point is I don't think that is particularly Pikachu's strong point in teams. Pikachu, I think, is a little better in teams than he is in singles because of his ability to get to anywhere on stage quickly and disrupt, create 2v1 situations, and help net early kills, especially with the assistance of his partner. There were a few times where your partner was noticably in trouble and you were content to continue your 1v1 instead of go to help out, which I think (not always, but usually) was a mistake. Again, it obviously didn't matter in the outcome of the sets, but I think that needs to be integrated more if you want to become a stronger team.
Your 1v1 fundamentals seemed good. You played to Pikachu's strengths, especially against spacies, found what worked against those players and stuck to it, and it usually paid off. I'd like to see other matches, especially ones that you lost or seemed to have a tough time with, as it'd be easier for me to assess what you could improve on.
Grats on winning grands as well! :D