Which of these, if any, is more correct unit vector notation?

Suppose I want to use $i,j,k$ unit vectors. Is any of the following formats more or less correct than the others? \begin{align} & (\textbf{i},\textbf{j},\textbf{k}) && (1) \\\\ & (\boldsymbol{i},\boldsymbol{j},\boldsymbol{k}) && (2) \\\\ & (\hat{\textbf{i}},\hat{\textbf{j}},\hat{\textbf{k}}) && (3) \\\\ & (\hat{\boldsymbol{i}},\hat{\boldsymbol{j}},\hat{\boldsymbol{k}}) && (4) \\\\ & (i,j,k) && (5) \\\\ & (\vec{i},\vec{j},\vec{k}) && (6) \\\\ & (\imath,\jmath,k) && (7) \end{align} In other words: is the hat necessary, unnecessary, or positively incorrect; and is bold math typeface any better or worse than bold text typeface?

Edit 1: Added Arthur's suggestions (5 & 6).

Edit 2: Added Tito Eliatron's suggestion (7).

While multiple approaches exist, I'll try to give an overview. One needs to discuss also how arbitrary vectors are denoted. Throughout, I'll overlook the option of bras and kets.

In handwriting (be it on a paper, blackboard or whiteboard), if vectors need to be made obvious through some formatting (this is more likely to be necessary if scalars and/or matrices are present and not suitably distinguished by e.g. being respectively Greek and upper case), this will use neither bold nor italics; instead one would use @Arthur's second approach (arrows on the top) or underlining. But unit vectors in an orthonormal basis are likely to be use hats instead of (or possibly in addition to) such adornments. Combining hats with arrows raises the question of which goes over which.

In print, you again wouldn't see vectors italicized, unless it's considered too obvious in context which things are vectors to go to effort with their formatting. The unit vectors in an orthonormal basis are likely to use hats in lieu of other indications, although if vectors are bold this will probably also apply to the aforementioned units, perhaps to the exclusion of giving them hats.