This letter tries to address the fundamental questions on the feasibility of multipath communication and achievable capacity for line-of-sight (LoS), obstructed-line-of-sight (OLoS), and non-line-of-sight (NLoS) scenarios in an outdoor setting for futuristic communication networks. In this context, a relevant measurement campaign at 300 GHz is conducted, and the results are presented in terms of the number of nontrivial propagation streams available for signal transmission. Encouraged by the obtained results, the average achievable channel capacity for such multi-stream channels is evaluated with and without passive reflecting surfaces (PRS). It is observed a multi-antenna system provides a significant improvement in average capacity compared to a single-antenna system with PRS providing additional enhancement.