How do I ensure my weldments always accept weld at their interactions.

This is hard to answer without images and more detail about your tube OD. And ID., but if the tubes are mated tangent to each other it should be as simple as a fillet weld, selecting the OD of both tubes (one in each bead set) and picking you weld size. The welds won’t go all the way around but should generate something. The Inventor forums would provide a better medium for asking this question.