10X is enough for most work but more magnification (or younger eyes) may be needed to see really tiny details. The chart below compares different magnifications:
My OptiVisor has the 10-diopter lens (3.5X) when used alone. Swing down the OptiLoupe and the magnification is 8.75X. Not nearly enough for me to inspect the .0625" (1.59mm) end mills used used to mill trit slots. Either a 2X or a 4X magnifier, placed between the work & the OptiVisor, gives 17.5X or 35X.
17.5X is sometimes enough if the lighting is just right. These are 4-flute tools & it's tough to pick up the tiny edge details that determine if the tool is good for another go.
Both my welding helmets have an OptiVisor lens plate attached to the inside of the viewing window. For in-shop welding a 2.5X plate is used. For portable welding a 2.0X plate gives less magnification but wider field of view: