Yes, you can absolutely add two checkboxes and a dropdown menu in the same form. Use select_multiple for checkbox questions and select_one for dropdowns. Structuring it properly in an XLSForm helps keep everything organized.
There’s a similar discussion where someone needed to show a select_multiple question right after a select_one, and the community offered a clear XLSForm solution that worked great—check it out here: Select_multiple after a select_one
