Hi! I would recommend some programs for quest makers. These are the ones I use (I won't give the links, but you can find them using google).
For sprites I use Aseprite. It is free and very intuitive (much simpler than Gimp to use), although it only has basic tools.
To create 8-bit/16-bit sounds I use sfxr, which is really easy to use. After the sound is created, it can be improved/edited using Audacity (I use it to change the volume, copy/paste/delete some parts, and convert the sound to ogg). There are other similar programs that could be useful, but I only use this ones.
To compose retro music, with sounds similar to the SNES, (and also to create some complex sounds), Famitracker is a very nice tool. I recommend it a lot, but it takes some time to learn the basics (there are lots of tutorials of other people in youtube, although only few of them are useful).
(For the code, Notepad++ is wonderful and very customizable, although you know it for sure.)