As a fairly long-term lurker of the community I feel somewhat invested in it's future and would like to add my two cents with the proviso that my opinions should always be considered secondary to the runners' own. I think that the primary issue with taking any no manip category seriously is that it is impossible to validate whether or not somebody manipulated during such a run, intentionally or otherwise. Moreover, no manipulation is kind of arbitrary a description in itself - everything a player of FM is doing is inherently 'manipulating' RNG, just not necessarily in the most efficient way possible, which is what the new route is trying to do. For that reason alone, calling the new route anything other than simply 'any%' would be somewhat farcical.
Due to that, as I've seen mentioned by GFC here, any separate non-manipulation category would have to exist on honour alone and while that has always been the case in the FM community to an extent, I would argue that the documentation and ongoing research into the new manipulations would make it an inevitability that someone would come up with a subtle way to utilize this knowledge subtly;during a potential 'Legacy%' run eventually. I will admit that that is a somewhat cynical perspective, but it does strengthen my belief that any Legacy% leaderboard should not be on an even keel competitively with Any% and as such I would be especially opposed to Any% being sub-categorized, largely due to the fact that it seems to be aimed more at placating those who still intend on running 'Legacy%' than upholding competitive integrity. While speedrunning, and gaming in general, should always be predominantly about having fun, when a competitive aspect is introduced, it needs to be respected, and, ultimately, though it saddens me to say it, what is being politely called 'Legacy%' could just as easily be called 'Arbitrary%' had it not been seriously run for years prior to a new route being discovered.
That said, I am not against 'Legacy%' having it's own category, I would prefer it in fact, however I fail to see how it can be considered any more than miscellaneous in nature. My recommendation would be that those who would be interested in running 'Legacy%' vote between having a miscellaneous category or RNG Manipulation Yes/No. I think both cater to the wishes of the new Any% runners, so it should be left to the 'Legacy%' runners to decide for themselves. I am absolutely all for fun and novelty-orientated speedrun categories and I believe that is the place 'Legacy%' holds in comparison to the new any%. That said, I believe the community leaders will make the right decision, and I'm looking forward to enjoying many more runs and races in the old and new styles in the future. I hope no comment in my post was too blunt and would once more like to assert that all my opinions are a mile's credence away from the runners' own.