This study analyses the results of two parallel two-month online exchange projects launched during the spring semester of 2018. The first project was a bilingual one-to-one English/Spanish exchange project for undergraduate business students. The second one was a monolingual one-to-many intercultural practice in English between native and non-native undergraduate business/economics students. Whereas both projects followed a similar structure, they differed in many aspects. Our mixed-methods approach focusses on student profile, project and task design, implementation, and coordination, in relation to students' participation, performance, and their evaluation of the project. The objective is to identify what led to positive (lights) and negative (shadows) outcomes and to provide a collection of project design recommendations to telecollaboration practitioners. [For the complete volume, "New Educational Landscapes: Innovative Perspectives in Language Learning and Technology," see ED596359.]