Do you have recommendations on how I should orient the modules to optimize RF performance? Is it a risk to place these two modules close to each other?
Each module should follow its recommended layout as best as possible with respect to placement and required ground planes.
For two modules, place them as far apart as possible. Note that the Rigado RF certifications (FCC, IC, CE, etc.) are indicated for a single transmitter. When additional radio modules are in use, they must not transmit at the same time as the Rigado module.