How to resize the ClipPath area of SVG?

You can apply the SVG as a mask and easily adjust its size and position (like you can with background-image). Simply make sure you set the correct value for the viewbox:

.img-container {
  width: 300px;
  height: 300px;
  background-color: lightgreen; 
  margin:5px;
}

.clipped-img {
  width:100%;
  height:100%;
  display:block;
  object-fit:cover;
  -webkit-mask:url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 207 167"><path d="M199.6,18.9c-4.3-8.9-12.5-16.4-22.3-17.8c-11.9-1.7-23.1,5.4-32.2,13.2c-9.1,7.8-17.8,16.8-29.3,20.3c-20.5,6.2-41.7-7.4-63.1-7.5C38.7,27,24.8,33,15.2,43.3c-35.5,38.2-0.1,99.4,40.6,116.2c32.8,13.6,72.1,5.9,100.9-15c27.4-19.9,44.3-54.9,47.4-88.6c0.2-2.7,0.4-5.3,0.5-7.9C204.8,38,203.9,27.8,199.6,18.9z"></path></svg>' ) 
               center/contain no-repeat;
          mask:url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" version="1.1" viewBox="0 0 207 167"><path d="M199.6,18.9c-4.3-8.9-12.5-16.4-22.3-17.8c-11.9-1.7-23.1,5.4-32.2,13.2c-9.1,7.8-17.8,16.8-29.3,20.3c-20.5,6.2-41.7-7.4-63.1-7.5C38.7,27,24.8,33,15.2,43.3c-35.5,38.2-0.1,99.4,40.6,116.2c32.8,13.6,72.1,5.9,100.9-15c27.4-19.9,44.3-54.9,47.4-88.6c0.2-2.7,0.4-5.3,0.5-7.9C204.8,38,203.9,27.8,199.6,18.9z"></path></svg>' ) 
               center/contain no-repeat;
}
<div class="img-container">
  <img class="clipped-img" src="https://picsum.photos/id/1074/800/800.jpg">
</div>

<div class="img-container" style="width:500px;">
  <img class="clipped-img" src="https://picsum.photos/id/1074/800/800.jpg">
</div>

<div class="img-container" style="width:150px;">
  <img class="clipped-img" src="https://picsum.photos/id/1074/800/800.jpg">
</div>

CSS mask with SVG clip-path