Where is the best location to place resource strings? Does it depend on scope? Currently most of our strings are being placed at the project level, but certain strings are
You should strongly favor using resources at the form level (set the form's Localizable property to True in the designer). The designer has very good support for it and the WinRes.exe utility is available to localize strings off-line. No code is required.
Localizing project resource strings is possible but not well supported by the IDE. Check my answer in this thread for an approach.