How do I choose a laptop if I'm interested in learning and applying data science?
This is a bit off-topic and very subjective. It is subjective as it depends on what you want to achieve. I am answering because I have been in this journey for the last 2 years and I can confidently comment 


  You certainly DO NOT need a high-performing laptop to start off with data science/machine learning.


based on the following reasons (at least not for the first year or two):


Building the foundations of machine learning, statistics and programming takes longer time that you may think (your objective is solely learning), till you get to do heavy deep learning optimization on images etc. 
Even if you get to heavy tasks earlier, there is increasing availability of free clouds like Kaggle, Google Colab etc. that you can run heavy jobs. Yes, runtime on those clouds are at present limited (e.g. as of now it is 1-hr GPU computing at Kaggle), but this will change really soon.


Thus, you are good with a laptop with 1TB hard-disk, 16GB RAM and Core i7, surely depending on your budget lower specification like mine (MacBook Pro 256GB, 8GB RAM, Core i5) also works just fine, unless you have more money to spare.

P.S.: I admit not being able to work on some image-based ML competitions in Kaggle due to limited computing power, but that time (~ a year ago) free clouds were less available. 

By the way, Welcome Onboard!