9 "main" categories if you wanted to separate difficulties but i'm not sure how you could make it look accessible. One possible solution but surely not the only.

-any% easy, normal and xtreme -all stages any% easy, normal and xtreme -100% easy, normal and xtreme

I know it is against what you are doing right now, but why not have all versions/difficulties available for view even if some are initially hidden(Emu and/or XC possibly)? Maybe state in the rules or somewhere that there are time differences among versions/difficulties. There is no reason to alienate emu runners from the leaderboards, they are part of the X6 community as well.

My reasoning behind this: -speedrun.com is one of the go to places to see ALL available runs for me in plenty of other games. -you could put them all together so there is less clutter, granted you are already showing version and difficulty. There are far too many variables as is between versions/difficulties. -PSX and XC separate categories I don't get. Time differences, of course they are there. I have to agree with peterafro on this. We already have mmrta separating them making it harder to navigate the site for newcomers -it is unfair to emu runners who are arguably good at the game to not make their runs available. Other X6 runners will know if your run is "good" or not so I would not get caught up on a better/worse WR or PB being done on emu