As a vocal coach myself I always say that Taylor is extremely underated as a vocalist and it is mostly because people who have little knowledge of vocal technique think belting and runs is what makes someone a great vocalist. She is an amazing technical vocalist (especially the past few years) with amazing breath control and with her vocal intonations, vocal inflections, vocal control and her ability to move seamlessly between her chest voice and head voice, and lastly and most importantly her cadence is hard for others to manage.. That´s why so many other amazing vocalists have a hard time singing her music, because it requires all those things and breath control through all those words and cadence and still evoke all that emotion that Taylor does.  
I remember how Rolling Stones wrote an article about this, after the Taylor songs tribute show on American Idol, how badly it went for all these "great vocalists" to try to sing her songs well..
I love her voice, it has this healing quality and so beautiful regardless if she is betling in one song and sínging softly in another.
Taylor just loves music and making art, that is her motivation for her music and you feel it in all her music, and in the interview that was before this performance (on the Grammy channel) she talked about that. I Highly recommend you watch the whole session of that great interview.

There’s something about her voice that just pulls you in and starts all your emotions.  So good

I think it's a combination of natural talent and experience.  I also think her voice control
has matured throughout the years.

You won't see others do this because they  can't. No autotune, no backup, just a piano or guitar, just Taylor can pull it off. She is the best.

I imagine that this mashup is probably an example of what it sounds like in Taylor’s head all the time. It’s so great.

She had 3 songs August , I knew it, and All Too Well. She is a genius

Such a beautiful mashup about memory! I agree, Taylor knows how to get the most out of her range, her breath control and wringing every ounce of emotion out of incredible lyrics.

Utterly unique. There is nobody like her

I love this. The full interview about her songwriting was 49 minutes, it was so interesting. This acoustic medley is about 6 minutes.

its her lifetime of experience and talent. she s a MASTERMIND

Pure goosebumps! All over! And Im speechless!

I suggest watching the full 45 minute conversation she had before this. Very enjoyable conversation and she genuinely loves her job and I really do think some of the things she said could help struggling songwriters.

I hope she puts out an acoustic album of mash ups they were all so good during the eras tour!

Taylor is a masterpiece ❤

Not every singer is a belter powerhouse. her voice brings the lyrics and emotion to life!   It's ethereal ✨

This is stunningly beautiful,.....shows off her craft perfectly.Her voice sounds incredible.
I too  love  cut back sessions ,l think you really see just how good someone is ,stripped back without all the lights and backing  singers etc.

I appreciate your respect for her.  Thank you!!!

You’re so respectful.  I loved your little reactions throughout but without overdoing it.

Taylor's performance is on her channel;  full interview and performance is at the Grammy  and Grammy Museum channel.  hope you react to the whole thing (yeah,  Patreon,  but I do that too).,

She introduces the mash up as 3 songs that are about REMEMBERING.