Yesterday, I happened to watch a Youtube video of Sabrina Carpenter perform at Coachella on YouTube.

Another way to say it, original is ok too

To my surprise, it/ Surprisingly, the video captured my attention the whole time./ throughout the runtime of the video, I was enthralled/ entranced by her performance.

I had listened to a couple of her songs on a Spotify playlist, but honestly, I thought she was an ordinary pop singer, a bit sounding like Taylor Swift, so I wasn’t expecting her to be such a good performer.

Small grammar comma hehe.

She hasd such fantastic/ amazing stage presence.

I had listened to a couple of her songs on a Spotify playlist, but honestly, I thought she was an ordinary pop singer a bit sounding a bit like Taylor Swift, so I wasn’t expecting her to be such a good performer.

I’ll definitely check her music out.

"check her music out" is completely fine, but I think "check out her music" is used a little bit more often

Her live vocals were surprisingly stablerong.

"Stable" sounds strange. I think you mean that her vocals were strong.

I had listened to a couple of her songs on a Spotify playlist, but honestly, I thought she was (just) an ordinary pop singer a bitwho soundinged a bit like Taylor Swift, so I wasn’t expecting her to be such a good performer.

I had listened to a couple of her songs on a Spotify playlist, but honestly, I thought she was an ordinary pop singer a bitwho soundings a bit like Taylor Swift, so I wasn’t expecting her to be such a good performer.

And the retro-style set also created a magical atmosphere.