Pharo is one of several Smalltalk “dialects.” Squeak is another. So are Dolphin Smalltalk, GNU Smalltalk, Cincom Smalltalk…for a more complete list, see my Resources. The IDE varies somewhat from dialect to dialect, but the essential elements are pretty much the same.
The Smalltalk IDE is very much different from IntelliJ and Eclipse, but I would recommend Pharo. Dolphin has a reputation for the best IDE in the Smalltalk universe, so you might want to check that out.
I’d say both Seaside and web2py are equally easy. The Seaside approach is unconventional so it may seem less easy, but it pays off in several ways. See my article, “The Heretic Web Framework.”