Normally, SONAR adopts whatever sample rate you used last as the default for new projects. Normally, all you have to do is open a 44.1 KHz project and the next new project you start will assume that sample rate.
Problems can occur if you have multiple projects with mixed rates, because if you open a 48 KHz project, SONAR will then assume that your next new project will be at 48 KHz, too.
The only solution is to get into the habit of checking the sample rate every time you open a fresh project, before you've added any audio to it. Eventually you won't have to worry about it anymore.
BTW, don't bother with 16-bit word lengths. It doesn't buy you anything except smaller exported wave files (all your intermediate files are still going to be 32-bit), and in some cases can degrade audio quality. So just stick with 24 bits for the audio driver.