I have my Ti Swift only for fair weather too. Because it's such a good frame, it makes sense to make the whole as light as reasonably possible and get a top quality ride out of it.

So, look at light wheels. There are some really good ones on Aliexpress for around $200 or even less. I would consider 451mm wheels but 406 is only slightly behind in terms of top gearing. You would need road caliper brakes for 451mm wheels. I just bought some Tektro R540 silver brakes, quite nice. For the Xootr frame you would need long reach brakes. I think road brakes gives a cleaner, less cluttered look.

For gearing, go 1x10 with 11-36t cassette and the Dee derailer. Just beware you will need Dynasys compatible shifters too.

The existing gearing though - it should be straightforward to get those working perfectly. The Park Tool website may be very helpful in adjustment and troubleshooting, as well as Sheldonbrown.com.