portability aside, is this 'healthier' for a battery fast charging than an old, now deprecated 29w apple charger (came with 12" MB's too I think)?
talking mostly for usb-c to lightning
presumably this is the one to get for MagSafe, since I think 29w only does like 13w or something whereas this should give the full 15w on MagSafe
The root of all the issues surrounding MagSafe and various power adapters is a disparity in matching capabilities resulting in compromised, limited compatibility.
MagSafe and iPhone 12 employ a new power level that only Apple's 20W and other PD 3.0 adapters can provide, to charge at maximum speed. If that last bit is not a concern, then an older non-PD 3.0 adapter would still work, in a limited fashion, at a stepped-down power level, which is what the various tests indicate.
Somewhat ironic, yes, that something like the 96W adapter has more than enough capacity to charge at 20W, but if it doesn't understand, or can't respond to the MagSafe in a way that the latter wants, then they have to play it safe, and go to a lower level compromise.
In summary: What a mess.
No wonder Apple canned AirPower. They're struggling with delivering constant 15w due to heat. Imagine the hot plate that AirPower would've been...
Don't conflate wireless charging, and the difficulty in AirPower's development, with a wired power conduit standard. They are two distinct and separate things.
The adoption of PPS for PD 3.0 allows for adjustments in both voltage and current, with fine granularity, which is what makes it an advancement over earlier specs. It also intelligently distributes power on multi-port adapters.
The new type of variable profiles (APDO) are much more flexible than the old fixed profiles (PDO) previous to 3.0.
To put it simply, the AI piece is correct in that adapters that conform to the newer PD 3.0 standard is what devices like the MagSafe and iPhone 12 require to operate at maximum power levels for the fastest charge.
While Apple, not unexpectedly, does not publicize the PD spec for their adapters, it's likely only the new 20W and revised 30W from August are PD 3.0. I haven't seen any tests of the '2020 30W to confirm, but its recent update without a change in capacity suggests it was updated in other respects.
The rest, including the 96W MBP 16" unit, and the original '2018 30W as well as the 29W, 61W, and 87W adapters, are not as likely to conform to 3.0.
Despite the 3.0 spec having been in the works for a few years, conforming products haven't started to hit the market until recently, and the new Apple products will help drive their adoption en masse.
