not sure how much faster, but powershielding a nair with the back against falco>dsmash can maybe be an option?, havent really thought about it that way...
In a world of perfect execution, this should be one frame faster than a shield grab. Without checking any data, I'm pretty damn sure this isn't enough to beat things like late nair/dair -> shine, and powershielding those would be very difficult in any case. The payoff for landing a grab is also generally much higher than that of landing a dsmash.
I think that consistent powershielding could be a way in on a lot of approaches, but if you mess up you could possibly die, also because nana shields late you would always have to be separated for it to be applied correctly, and if you powershield, she gets hit I believe its still possible to drop your shield and them get hit due to stun.
For basically the reasons listed here, I don't generally care for powershielding unless I'm Sopo, although there are exceptions to that preference.
I think powershielding has a lot of potential applications vs Marth, and vs Falco if you can powershield his lasers, or perhaps vs turnips in some occasions, and I bet powershielding would be beastly vs ganons aerials since you could powershield and immediately dash attack or maybe dash grab in cases where he would otherwise be completely safe, but we already have methods to make those characters approach us, so it's still somewhat limited IMO.
I can't envision powershielding being all that great against Marth. The only big advantage of powershielding over regular shielding is that you can act however you please after shield-stun ends, but unless Marth is spacing deep, I doubt you'll gain any significant advantage. The risk here is also huge, and trying this when Nana is with you will almost certainly result in her getting hit, notably weakening any punishment you can deliver. Most of this also applies to Ganon.
Powershielding lasers is okay. I do it as Popo, and I think you still can do it when synced provided that you're running forward so that Nana is a little behind you, although I think ICs have better and more reliable answers to lasers when synced anyways. I also don't envision powershielding being great against turnips, but it's worth looking into.
I wonder if powershield dash away bair is something we will ever see used to beat out dair/nair shine. If spaced properly could this lead into a grab or good tech chases vs Fox/Falco? This is just theorycrafting a bit but that would be awesome to see. Vector man has shown that it's at least possible with Yoshi to perfect shield into an aerial with at least some level of consistency, I would like to see where this could take us in some matchups. I am trying to think of how it could be applied to puff/peach/ganon/samus?/marth/fox/falco.
Dash away bair is too time-consuming to be practical for most purposes. It also generally has a lousy payoff, although there are exceptions. Yoshi has parrying, which functions notably different than powershielding and is generally easier to apply.
Picture this, Fox nairs you, you powershield, short hop, dair, then grab with nana since she would have likely been hit by the nair, into a tech chase/handoff. Would work beautifully at low percents in thoery.
Powershield -> short hop dair is no faster than a shield grab and has much worse payoff. Nana also likely wouldn't be in any position to grab after the nair unless she was at a low percentage and CC'd it. Even if you could get that to work, a standard shield-grab would be better since a Popo grab is much more reliable than a Nana one.
edit: I'm going to sleep now and will flesh out the guide when I wake up. It has seven main parts and I'm still entirely sure how I want to express certain things, but I think I'm sufficiently not stupid to work it out. It should be up before people in the GMT-{5,8} time zones who aren't on a crazy schedule wake up tomorrow.
