I'm not familiar with the greater community so I have no opinion on that matter, and I'll just mention that I mostly played in isolation with occasional chitchats with a couple other players (mostly Paddy), but I would like to offer some general advice.

As we've mentioned a few times in a few places, categories can get messy and deciding how different runs should be ranked together will always be subjective. Nonetheless though, I did try my hands (and feet) at 2-Player mode and it most certainly requires a unique skill and lots of talent. The co-ordination required to even take in all the information on two different screens of differently positioned vehicles moving at different speeds is quite the challenge to perform well!

I will always recommend to anyone to always first be playing for yourself, however that may be, even if it reduces your effective competition to just you and yourself. The reason for playing in such a way is important though. Is it because it is the absolute fastest? Is it because it is the most active? Is it because it is the most fun? Or maybe it's some compromise between those and other factors. In any case though, it's good to evaluate why you put the time into whatever it is you're doing and for what purpose. Enjoyment should usually be one of the top reasons. I personally would respect well-performed runs of 2-Player, ASB, NG, and other various combinations and categories, but for my own personal enjoyment, I kept things simple. Likewise, play what you most enjoy and think about what it is you're trying to do. Is lowering your own times for the sake of itself enjoyable? If it is and isn't at the cost of anything important, then go for it!

It seems like you've spent some time doing just that though, evaluating what you're doing, so I hope whatever decision it is you're making is well thought out and a healthy choice. At the end of the day, it's always your call how important speedrunning video games is.