The Transmission Control Protocol (TCP) remains the cornerstone of modern network communication, enabling reliable and ordered data delivery across a wide range of network environments. Despite its ubiquity, TCP’s variants’ performance under extreme and highly variable network conditions remains insufficiently explored. This paper investigates the behavior of two common TCP variants - CUBIC and BBRv1 - when subjected to dynamic bandwidth and delay fluctuation. Such conditions are increasingly common in real-world wireless networks and can have a significant impact on TCP flows. We conduct a series of tests using the ns-3 framework, employing a dumbbell topology to simulate wireless connections. The results of 6 different testing scenarios are presented. They showcase that both algorithms experience significant packet loss in the event of bandwidth variance in-transmission, with BBRv1 adapting to these changes better, but not dominating over CUBIC in a multi-flow connection. In addition, both TCP variants experience harsh throughput drops and lose very few packets in the event of delay spikes. When faced with both delay and bandwidth variance, BBRv1 experiences high packet loss while CUBIC’s connection remains stable.