A couple of clarifications -- you may be confusing source ports with editing utilities. Source ports (such as ZDooM, Legacy, etc.) offer features beyond those offered by vanilla DooM -- colored lighting, deep water, room-over-room, slopes, scripting, etc. Editing utilities come in different flavors. WadAuthor, for example, is meant primarily for creating and editing maps. DeepSea and XWE, on the other hand, may be used for map editing as well as managing other elements of a wad (known as lumps). WinTex is another example of an all-round wad manager and map editor.
what's a good transition period for moving onto advanced levels, in other words, how many levels should i make using DEU or Wadauthor whatever, before i try the advanced utilities, like several dozen or, just a safe ballpark figure
WadAuthor, DeepSea, and XWE all allow you to make and edit maps for source ports.
If you're comfortable with designing and creating maps for vanilla DooM, doing the same for a source port is not too difficult. I began working with ZDooM about a year after I began editing for vanilla DooM. I had done 6 regular maps and 8 partial conversion maps before I began my 5-level TC for ZDooM. However, I'm sure there are people who've jumped right into editing for a source port.
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