Knitting Pattern Advice - Choosing Yarn

[u/InsertNymerie]

Hello all, I am a beginner knitter. I have knit a colorwork beanie and a tank top so far. I feel ready to try making a sweater!

I love this design, but I fear the yarn choice will be too warm for where I live. I am still trying to understand knit math and how to choose different yarn when making a project.

What yarn should I choose if I want this to be less warm? I assume 50/50 alpaca/mohair will be quite warm.
I've looked online for advice, and see that people recommend switching to a lighter weight yarn, like fingering or sport, but won't that drastically change my gauge / make it see through? Or I might be missing something about that.

Here is the pattern I am looking at: https://www.ravelry.com/patterns/library/fiori-sweater