I tend to format CASE using indents (tabs) for the different lines.
SELECT
case
when x = 1
then 10
when x = 2
then 20
else 50
end 'my col'
As far as the GUI. Personally I do not think it works well for complex SQL, but that's me. I understand why people use it, but with outer joins and unions and cases, it falls down (to me). When I truly need to debug, it is often from Profiler or embedded SQL in an app and the the GUI doesn't really help me. Too slow. Don't really have a recommendation here because I do not use it.
I don't upper case the keywords because I'm lazy. Grew up on Unix/DOS and prefer lower case for most things. However, you should do what makes sense for you and be consistent (standard) for others in your environment.
Steve Jones