@ rvo_nl
Oops! You're right, that outline option isn't there. It was added in 4.0. My mistake

For a default look for all your drawers, set up a drawer how you like it, snapshot, and copy it's .info file to ENVARC:Sys/def_drawer.info. From then on, all new drawers you create (and those without their own icons) will have those settings as default.
As to scrollbars, it sounds like you'll soon have Visual Prefs working (that AmigaOS3.5: reference is probably just from a badly-configured config file that uses absolute rather than relative paths), but I'm attaching some screengrabs of MUI prefs. They're from OS4, though the standard and custom views will be identical under 3.x. OS4's GUI prefs (analogous to VisualPrefs) are responsible for the look of newlook.
The AslPrefs in WBStartup reference you found has to do with an ASL replacement/patch from before the OS3.5 era. You don't need to worry about it.