Achieving larger images with smaller file sizes (for the web) with Gigapixel

As I using Gigapixel for creating a web photo gallery and not printing, I am looking for the best procedure to control file output size. It’s easy to increase pixel dimensions for the output, but inside the standalone Gigapixel version, I don’t see any control of final file size output. Obviously this would be easy to control from inside Photoshop, but I have been unable to install the Photoshop Plugin into Photoshop 2022 (v 24.1) and so I have no access to the Gigapixel plugin. Therefore, it seems that my only option is to create the new size image in Gigapixel and export to Photoshop once again to reduce the file size. I’ve searched for info on the reduction of file size output but I don’t see anything listed.

Is there something in a knowledge base or something in a previous thread that will provide me with a better understanding on this subject? I do love the results of the sharpness when increasing the image size, but since I am not printing but only using the files for a web photo gallery, I need to the final image size down of the enlarged images. Any suggestions are greatly appreciated.