I'm not sure about what to do at YXE (I could tell you all about YQR...), but will suggest that you try to get a seat assignment as close to the front of the plane as possible so that you can be further up the immigration line. The last time I went through DEN from YQR in the afternoon we were delayed by 10-15 minutes and that put us in the immigration hall with an LH flight. I hoofed it off the plane and to immigration, and just narrowly missed being at the end of a long long lineup. Other times, we've been ahead of that flight and immigration is a cinch. I think the YXE flight comes in 30 or so minutes later than the YQR flight, so be aware of timing.