Hello,
Let me take your questions in order:
1. Yes, and you have all the information to program that! You have the elapsed time in seconds, so all you have to do is compute what that is in terms of hours, minutes, and seconds. Since this is trivial to implement, and I know you are at the beginning of the learning phase, I implemented it for you (see the attached new Example - it still uses the stopwatch subVI of course, but you should still have that, or just see my previous post to get it).
2. For the stopwatch subVI, you should keep the enum, since your users will never touch that. For the example (application level) interface, you can use whatever interface you'd like. The enum is convenient, but you could use a set of radio buttons for example, where they would click the selection they want, and that way the actual selections can be spaced (you can move the radio buttons as far apart as you'd like). I'll leave that implementation choice to you.
I hope this helps you further!
Best Regards,
JLS