Newly inserted images will have the dimensions of their source file unless these dimensions are larger than the screen in which case dimensions will be decreased to allow full display.

Setting one dimension (Width or Height) of images either by drag-and-drop either using the image context menu will update proportionally the other dimension according to the dimensions of the image source file unless the Images Distortion option of the page context menu is enabled:

Any type of line-up will not affect domensions of images but only positions.

Images can be brought to proportionate dimensions according to their dimensions in the source file using the Resize options of the image context menu:

Use File Size will set the dimensions of the image as in the source file.

Adjust Width will keep the Height as it is and adjust the width proportionally according to the dimensions in the source file.

Adjust Height will keep the Width as it is and adjust the height proportionally according to the dimensions in the source file.