Hi Micke and welcome to Piwigo forums,

Micke wrote:

If I use the build in "upload photos", the images are "pop-upable" to full size; something I do not wish.

However, if I use "Ploader" it works just fine with the resizing to the size I wish.

pLoader and the upload form do not use the same resize settings. By default pLoader does not send the high definition photo (HD size).

With Piwigo 2.1, the upload form does never remove the HD. This is a technical constraint because the server side resize removes the photo metadata. With Piwigo 2.2, we are improving the resizing algorithm and we will be able to remove the HD.

What you can already do with Piwigo 2.1 is to hide the HD :

1) go to screen [Administration > Users > Manage]
2) select a user
3) Properties > High definition enabled : set to "No"
4) Submit the form