Charlie.
In order to test welders, qualify procedures or do production, it is critical to have a copy of the applicable code on hand.
While you may get the correct data from asking questions here on this web-forum. The best way to work through your qestions and the best way to have a good quality program is for supervision to have the code on hand at all times.
Getting confirmation on this site is a good way to validate what you discern from the code book, but if you don't have the hard copy reference you risk confusion and non-compliance. Especially when dealing with multiple codes.
The thickest bend specimen I have seen is 3/8". Once the base metal thickness exceeds 3/8", side bends are used which are 3/8" wide x the base metal thickness. I think 3/4" is the maximum base metal thickness allowed for face/root bends, but I've never seen anyone choose to do a face/root bend on material over 1/2" thick. When the base metal thickness exceeds 1-1/2", the side bends are allowed to be cut into multiple specimens. The "standard" width of face/root bend specimens is specified as 1-1/2" in ASME IX and AWS D1.1, however narrower specimens are allowed for some pipe diameters. Not sure if this holds true for other codes, but I doubt there would be much difference. I think they are all based on the ASTM A370 bend test requirements. If you make it to accept specimens up to 2" wide, it is not likely you will ever need to cut specimens into multiple widths.
Most basic benders are set up with a die radius for 3/8" thick face & root specimens or 3/8" side bend specimens. You have to remember to not use this radius for face & root bends in material less than 3/8" thick though. The die radius is always 2T, which is 2 times the specimen thickness, or die diameter of 4T.