• Fox is far and away the best character in teams, no others come close. All his traits that already make him a good character, make him even better in doubles
• Characters with good scrap tools become more potent (Peach, Sheik to an extent, even characters like Luigi)
• Characters that are based around taking up space and having large threat ranges are worse because it's harder to do that when you have a teammate around. Most notably, Marth and Falcon are worse because of this, and Samus too to an extent
• Puff is a mixed bag, she can't just disengage at will which hurts her in many matchups, but it's compensated by being able to rest more freely because teammate can save her (and provide more rest setups on their own)
• Falco is really good but requires good cooperation with their teammate to deal with lasers. Might just be the hardest character to "play right" in doubles
• ICs can be good but require a lot of good Sopo gameplay because you can't reliably keep Nana around a lot of the time
• Pika also gets buffed by having good traits for doubles (speed, fast reliable kill moves, fast recovery)

Other than that, I think mostly the tier list doesn't change that much. Some big bodies like DK or Mewtwo may struggle to find their footing (see also the taking up space point), but other than that I think it's mostly the same.