1) XenForo quick search
"Search Wiki only": In XenForo 2.x, this could be simplified to just "Wiki" (or title of the wiki, e.g.
Wiki XF for XF demo at
https://www.vaultwiki.org/xf-wiki/ )
If you browse around XenForo.com, they use short phrases for search constraints, such as "Threads" for forum posts and "Resources" for XFRM items. I believe that these are worded to make sense with the adjacent "Search..." textbox. E.g. Search...
Everywhere, Search...
Threads, Search...
Wiki.
"search_only_x": While looking at an Area or page, this phrase is missing. I assume this phrase is from XF1 e.g. "Search this area only". If you adopted the XF2 approach (e.g. "This forum"), then VaultWiki could say "This area".
2) XenForo advanced search
"Search in areas": XF's "Search in forums" combo box uses a double space to denote a child instead of the double dash (plus one extra space between level 0 and 1). I can see why the double dash was used for VW though, since this is how XF does it in the admin cp. Truth be told, I actually only just realised that XF represents the forum hierarchy differently on the public search pages and admin cp just now

.
Comparison (Public search vs Admin):
Code:
Index
Child
Child of child
Child
Code:
Index
-- Child
---- Child of child
-- Child
Tabs order: Personal preference, but I think "Search Wiki Pages" ought to be positioned
before "Search Wiki Discussions" as this would then match XFMG order (Search media
then Search media comments). VW4.0 on XF1 the order had the VW pages tab first.