I don't see how Matt putting out fitness videos in any way would step on Jade's toes, maybe her ego though! Those types of content are also very straightforward and less about chatting and life updates if any at all. I do many yoga and stretch YT vids and it's just the routine and nothing more-which is what I like and want anyway, so HIIT workouts from Matt would be ideal with none of the stupid fluff. As time passes I can't imagine either of them will be concerned at all with what the other is doing on SM - but Jade would be monitoring Matt and be jealous if he did well that's for sure.
Jade hitting 100K and not acknowledging it was a team effort was maddening and is another instance of her just being a self-centered jerk.