Gym guys and girls, help me?

Hiii! For all the gymrats out there, I need your help! First a little back story of me, about my physique in the past. Right now I am 20 years old (F). I am 5'8/5'9 tall and 145lbs. As a child, I was always severely underweight. Not because I wanted to, I just couldn't gain weight no matter what (probably because I kept growing lmao). When I was 17, I was 5'8 and only 100lbs. I used to pass out all the time and didn't feel good in my body at all. But I did feel special. Not many people were as skinny as me. Once I turned 18, I started gaining a bit of weight. I quit my sport and started taking birth control (for health reasons). Now 3 years later, I barely recognize my body. I'm definitely not fat, but my belly has started to show. I would like to become fit again and lose some weight. I do not want to return to my past weight! Because I wasn't healthy. My goal is 120lbs with a toned body. I want to be slim again.

I've been doing workouts from 'Nikola's pilates' on yt for the past 5 days. I'm wondering if anybody knows whether they are good workouts? Because I want a workout, that does not make me look bulky. I want to be slim. I do want muscles to look toned around my arms, legs and waist, but I do not want a sixpack! I will show some examples.

Gym guys and girls, help me?

As pretty as this women above me is, I do not want the muscles like this. What I want is more like this:

Gym guys and girls, help me?

Do you guys see the difference? This one has those lines of muscles, and not really that bulky effect (I don't know how to explain it lmao). In the past I used to look like that, bc I was just so skinny that the little muscles I had were showing. This time I want it to look like this in a healthy way, due to the muscles that I'm growing. But only those muscles. Not the other. One more thing:

Gym guys and girls, help me?

She is also super pretty, but I don't want my arms to look like that, more like this:

Gym guys and girls, help me?
Gym guys and girls, help me?

Please help me with advice. Thank you all!

Gym guys and girls, help me?
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