Holes too close to a bend will pull and distort. The larger the hole, the more it will distort. As a rule of thumb, place holes to leave at least 3 times the material thickness from the edge of the hole to the outside of the bend. For larger radii bends, use 2 times material thickness from start of the inside bend radius.
There is a minimum height that flanges can be formed to. The actual values vary, but as a simple guideline lets say the minimum flange length we can produce is around 4 times the material thickness.
Bend relief of flanges should be considered when designing parts. Flanges will not form properly when the flange is placed inside the profile of the part. The flange either needs bend relief notches or the outside of the flange must be at least a material thickness (preferably a material thickness plus the radius) outside the blank.
The edge of a hole or feature should be at least one material thickness away from any other holes or edges. This can be made slightly smaller in materials like aluminum, but not too much. A web that is too small could result in a bulge or the need for a secondary drilling operation.
Punched hole diameters when possible should be no smaller than the material thickness. Creating smaller holes requires prick punching and drilling, making the parts more expensive.