If I install Civ III Conquests, am I getting all of the features and functions (including the editor) from CIV III PTW?

Does Conquests contain the fixes from the patches for PTW?

I guess, I'm asking if you can skip PTW and buy Conquests and not lose anything?

And, if you have PTW, are there any differences that would invalidate scenarios and customization to files like resources, units, etc.?

Conquests will come with PTW v1.27f (the latest patch) on the CD.

You should lose nothing by going straight from Civ3 to Conquests. (Except for the fan-made scenarios and stuff that came with PTW, but you can download all of that from CFC, Apolyton, and CDG. ;) )