The black bow tie defines an entire style, and as such deserves a bit of respect. Pre-tied and clip-on models are simply out. A fixed-length tie of a length appropriate to your neck is always preferable to adjustable models as well; the latter will have excess fabric that doubles over and adds an unsightly bulge to the knot when tied. To keep the tie proportional to your face, try to make sure that the ends of the bow fall somewhere between the edge of your face and the outer corners of your eyes -- anything smaller will make your head look oversized. The material of the tie should match the jacket's lapel facings visually; shiny ties with soft-fronted lapels will create a glaring breach of the outfit's uniformity.
A bespoke suit that doesn't fit at all the key points is a suit that's making you look silly in at least one place. You can't really afford even small gaffes at a high-stakes interview, so have your csuit adjusted if it wasn't tailored to your measurements in the first place: the sleeves should fall to the base of the wrist and leave 1/2" or so of shirt cuff visible, the lapels should lie flat when the jacket is buttoned (which should not cause any pinching or bunching at the waist), and the bottom end of the jacket should fall far enough to cover the curve of your bottom. The collar should lie flat against your neck, with 3/4" or so of shirt collar showing above it.
As with any clothing measurements, the best judge of fit will always be trying the suit on. Make sure that it rests without pinching or bunching even when you move, and that the fabric is not loose enough to fold or billow on its own. Anything that causes discomfort or unattractive wrinkling should be fixed before any interviews.