Okay maybe I wasn't
quite right about just needing Sam Speed slowed down for vanilla characters being able to clear VS. Sam Speed.
I saw a video of Adventure Sonic's Rush mode and that reminded me that exists and made me want to try it there, and
A. It worked and was fun as hell, aside from one frustrating spot
B. It made me realize that aside from the first two straightaways, Sam Speed isn't
that fast? You could probably just make those downhill or something instead of checking for X-Sonic, if you'd prefer that? Does X-Sonic benefit from going downhill? He kinda just seems to either trot at a "feels slower than that honestly" 25 Fracunits or zoom off at 90-100 with nothing in between . . .
C. That one spot and exploring the racetracks after the fact let me see other places where vanilla can't handle it. I took notes? If you're interested, if you want to keep it "X-Sonic and maybe some other mod characters by coincidence only" that's obviously your choice.
First is this cliff in the first wilds area. The obvious thing would be a spring here, in this spot where the path leads you and X-Sonic has to run up the wall, while Rush Sonic has to do a totally sick slope jump that vanilla Sonic just can't make.
But personally I think I'd prefer some springs along this cool platforming path that has springs for like, half of it, but is just barely too tall for vanilla to start on it and just kinda stops having them halfway up the cliff?
There's likewise another "there's springs for part of a path, it looks like there's a path, but then there's not? Once you get up the cliff, but it's less important because you can also just sorta run along the other obvious path.
And then a thing that took me a bit but is probably a somewhat easy fix, vanilla Sonic and probably lots of other characters can't make the jump across the big ravine in the desert alone, but exploring around after the race I found Sonic's friends ready to throw him across off the road a fair distance. You could probably just do a fork in the road there for conveyance, as an added bonus it'd make taking the jump for super fast characters like X-Sonic feel a little less like "this is the path the game wants me to take" and a little more like "I bet I could take a huge shortcut there."
(If the lighting feels a bit wrong in that last screencap, it's because I tried loading up the "day/night cycle" mod while I was exploring the desert because the music and vibes post-race are just so chill. A bit "feature request" and entirely superfluous, but if you wanted to make it night for post-race exploration, that would be really great.)
Also a slight bug report, but it's also another mod compatibility thing, and probably a multiplayer thing but I haven't checked:
The Metarex hitting a Foxbot or presumably another player knocks back Player 1 like if they had gotten hit.
(Mods used during testing:
The Meter, because I like seeing my speed.
Foxbot, to switch characters quickly.
Antimetalsuffocate exploring the desert.
Day/Night cycle for a bit in the desert, didn't look great.
Also currently technically on The Story Of Uncapped Discord Revengaence The 3rd because this mod has a ton of slowdown in the current 2.2.14 and that's the copy of 2.2.13 I have installed with my full mods folder that, come to think of it, is kinda unnecessary for this but still.
Pretty sure none of these would have made a difference here)
((Also I haven't posted images on here much before, so sorry if the resizing in the editor made them hard to make out or if they're too big and taking up too much bandwidth or something)
--Edit
Also I seem to recall you saying you were planning to make a character to go with, originally planning on Whisper as the "canon" PC for Sol Sestiancia, currently leaning towards Sonic in your style, mostly because other people wanted it . . .
might I suggest that sick battle damaged / Master Asher corrupted(?) Metal Sonic that's the final boss, instead? That thing is so cool. 
