No, you don't need to make a new channel strip. You'll find out as you work through the UB tutorial, but basicly you can create more than one pattern in UB. Once you've created your patterns, you can either leave them in UB or drag them onto the arrange page where they magically turn into new midi regions.
So you can either take kicks out and add more hats using UB's patterns, or else you can copy and edit the midi regions in the piano roll.
Personally I use UB to build the kit from samples, then create a basic pattern, then drag the pattern into the arrange window to create a new midi region. Then I can loop, copy and edit the region any way I like - open the piano roll and add more hits with the pencil tool, change the velocities of different hits, change the quantisation etc.
What works for you will come down to your workflow, and you'll have a much better idea about what you can do once you've worked through the UB tutorial.
As for frequencies:
Drum kits are great because as they've evolved over many many years they are already designed to fill different frequency ranges without the separate elements clashing with eachother.
For example the main body of the kick is around 50-60 Hz, and hit hats and cymbals are high up in the 1000s of HZ. So without you having to do any work, a hi hat and kick drum played at the same time are both going to be audible.
The thing to remember is to use low cut EQ to cut out the low frequencies of each of the drums. You don't have to do this until you mix. I'd recommend Olav's Mixing electronica to teach you about the mixing process.
And tune your drums! Its really important and its surprising what a difference it makes to tightening up a track.
Hope that helps!