Get some foam cushions you like the sit on and have them done with a fabric you like . I think you are the only one who knows what is good for you. I will say those cushions you show would IMO not ever be comfy.

Oops, sorry, those aren't the cushions, that's just a chair from our teak table set.

You need to work them in! Cushions will soften over time.

The expensive cushions that have the quick dry foam/filling never soften over time, but they do last a long time, even when exposed to sun, heat and humidity.

Look for cushions with a zipper and add batting.

For more comfort, hire a seamstress. Good cushions are very expensive and having made can be less expensive. My sister has done this a few times and it was cheaper, she had her choice of the filling and by buying fabric, it opens up all kinds of Sunbrella choices.

Below is a link I thought might be helpful. https://m.youtube.com/watch?v=1-HEjSW9qAA