Unfortunately, I'm making do with an iPad at the moment, so cannot check, but neither of those things should be an issue in GIMP. It sounds as if you're mixing the crop tool up with canvas cropping. I hardly ever resize the canvas, but if I recall even that function, accessed from the menu I believe, is quite well done. If I recall, you specify a size in percentage or whatever measurement you want, and it will ask you where you want to position your current canvas relative to the new one. For example, you might want it to stick to one specific side or corner instead of the middle.

Regards the popup, it sounds as if you need to experiment with customising the interface if you want that thing in a specific permanent place. To give you an idea of how customisable that stuff is in GIMP, here are just a few tips:

• Every tool in every in every palette can be added, removed, rearranged, added to new custom palettes, and even skinned.
• Every tool palette can be docked or floating.
• Every tab contained in every palette can be rearranged, added, removed, and even dragged between palettes.
• The GIMP splash screen can be customised.

Could go on for ages, but In a nutshell, you can make GIMP look and behave pretty much exactly as you wish, so I would start dragging windows, palettes, and tabs around and experimenting with various docking combinations. Try right-clicking on things like tabs and toolbars headers etc, which if I recall brings up more options. Also bear in mind that if you grab the edges of control palettes, windows etc, you can resize them and everything will be saved.

Before you do that, though, I would go into preferences and really study the depth of options under every tab, even the stuff tha normally would not interest you, because that way you will discover things that you would never dream they would allow you to customise. Just mess around with it, you can always go back to the default if you break something.