WHICH ASME / AWS STANDARD IS TO BE USED FOR SPECIFYING WELD EDGE PREPARATION ANGLES?

What type of weldment and code are you building to?

CODE IS SECTION VIII DIV 1.
WELD IS LONSEAM WELD FOR MAKING A SHELL

Weld edge preparation is not dictated in ASME Sec Viii Div 1.

Refer to UW-28 Qualification of Welding Procedures.

Being knowledgeable of welding procedures or find examples over the internet (Google) of industry acceptable joint designs for welding. Then use ASME section IX to write a WPS and qualify it by testing resulting in a PQR by which you will qualify your welders.

Hope this helps,
QCRobert