I have an wall that is about 2mm thick and 2mm wide and would be printed in FUD. It's connected to fully supports other walls and should be fairly sturdy. Length shouldn't matter, but it's probably about 10mm. My question is, I want to angle that full length at a 45 degree angle or bevel. If you can picture that, it would basically mean the width would start at 2mm thick and taper down to 0mm. Is that doable, or does is the taper considered wall thickness?
If I understand you correctly, you're talking about something like the yellow bar in this drawing: Whether that bar is 2mm thick or 1.414mm thick (perpendicular to one of the faces) then it should pass the thin "walls checks". The only problem will be is if it's length is much longer than 10mm, then it's going to sag some during cleaning (which is done under heat). Check the design rules.. there's some pretty good explanation of supported vs unsupported "wires". https://www.shapeways.com/design-rules/frosted-detail
At 0.3mm in from the pointy sides, the thickness will be 0.3mm, the pointy edge should print ok - As an example, the model pictured below printed just fine in FUD and WSF - the prongs are 9mm length and at most 1.25mm thick, the bevelled edges start at 0.75mm and taper to nothing. Slightly different to what you're after, but it can be done.