I would say, you already said everything! :D

In my opinion you should have at least 1 post, which should be your introduction, so that the people know who is commenting on their posts.
You should put much effort in you’re introduction and make it interesting.

The problem with just commenting but not posting is, like you mentioned,
The people see your comments, visit your blog and it is empty..
So I think they will nor often decide to follow your blog.
But if there at least 2,3,4 posts which represent your blog, the people will know what they can expect und start to follow you.
When I started I also thought I will build at first a base of followers, so that my post with much effort go into the empty space.
But then I decided just to start also posting.

I think at the beginning you should make a mix of both but concentrate more on comments. The frequency of posts can be a bit lower at first.
If you have enough time, you can also use the first posts for training sessions.

So didn‘t expect, I have something to add before starting this comment and now we‘re here 😁