To be absolutely honest, the difference is marginal in most (but not all) cases.
You probably won't even notice any difference in:
wide or baggy garments (like a tunic or pirate blouse)
garments where the shoulder seam extends far down the shoulder (like a kimono or most casual menswear)
garments sewn from stretchy fabric
Puffy sleeves that ...
The obvious solution seems like the best here. Sew it on by hand. This requires basically no sewing experience; if you can sew on a button you can do this.
Don't put the needle through the wire. Rather, put the needle through the fabric from behind, wrap it over the wire, and put it back through the fabric on the other side. This makes a loop of thread over ...
Do you want the shirt to actually be wearable? If so, then "synthetic resin varnish" is entirely the wrong option.
For wearable clothing, you need a color that bonds with the fibers to endure wear and washing, but also remains soft to allow for comfortable wear. The best option for something like this would be a standard acrylic paint with a high ...
There are a few things to be considered here:
Are you sure the drawstrings will be comfortable when lying down, either on your back or your side? If you aren't sure, consider pleating instead.
Will you be able to ignore the loose ends of the strings or will they bother you? You can keep them shorter than shown in the picture (sew them in place) or ...