That’s looking pretty good Jessie. I’d use the coverstitch. Don’t like twin needle but that’s just me!
Did you add width at the sides? If so, that would affect the armhole.
I usually say woven patterns for woven fabric and knit patterns for knit fabric. You can see why!
Even with those rules, you can come unstuck. You can make something in one fabric which fits lovely. Make again in something heavier or lighter and darts can be in the wrong place, lengths all wrong etc. And knits are a particular headache. If you make toiles, it’s often difficult to make one in a similar weight and drape so you have to use a bit of guesswork.
Glad that site was helpful. There are loads videos on fitting and pattern work there. All very good.