If you set the font, size, color, shadow etc. the same, not auto, haven't experienced any problems with anything not matching up. That said, for your application here's very briefly how I'd do it... I'm not sure you could exactly mimic a single line of text using text objects and text buttons in DVDA, and the following can produce better results with much more control over character spacing, outlines, shadows etc.

I'd create the menu background in Vegas, generating the complete lines or segments of text (with reduce flicker -- prog frames etc.) as an overlay to your intended graphic or video. Then I'd save a .png snapshot of the text overlay only, editing that in P/Shop or whatever to delete the portions of text I didn't want highlighted -- use this for your menu's highlight mask. You can do the same thing -- often easier -- in P/Shop (or many image editors), but Vegas will produce more legible text if your font sizes start getting small (IMHO anything < 16). For std. TV viewing DO NOT forget shadows for your text.

It's important that you keep an eye on aspect, especially when using stills for your background -- Vegas & DVDA can be overly helpful and change things on you if you're not careful, & that could lead to things not lining up 100% -- sometimes only on stand-alone players.