This is possibly a way to find all the bullet points and things you could be wondering about, consdierng how there's a lot of old and a lot of new that is scattered across knowledge of players, but not really anything that has everything in resources for a beginner to pick up and start mapping.
Even if you have SRB2 and SRB2Kart mapping experience, there's some things that you'd need to know from the official mapping guides or talking with other mappers, such as how to do waypoints, what you can do with Bot Controller, and things you can use to handle certain quirks introduced by RR.
You got High Voltage Ring? No? Then FIRST, when you download and install HVR, if it is still in Version 1.0 [which it is, as of writing this], you have to go to the folder where its installed and rename ___ to UDBuilder.cfg for the program to launch...as it otherwise refuses to open while asking for that file.
Now what, huh? Open the editor, click new map, and start editing and then- nope. There's still more setup you have to do.
The handling and controls weren't very altered as with the Riders mode, and instead played closer if not virtually like re-skinned vanilla SRB2 gameplay but without normal jumps. You could hop but not drift, items were completely random (regardless of position), didn't have the single player bots, and you could even cut over off-road without a speed loss by hopping over and over with the right timing.
There are other details I noticed from investigating this build, such as...
Even though it isn’t possible to confirm this due to how the older versrons can’t be found anymore, it seems that the first Riders versions with the Mario Kart mode might only have included 8 maps made by CZ64, Chromatian and FlareBlade.
This is because out of the 10 tracks that were seen in this last version, two of them actually had standalone releases in the Message Board in 2009 intended for the Mario Kart mode: Crawla Cape by Violo, and Dusty Dunes by DaicheS9. It is possible that they were noticed by CZ64 and added to the mod, which is doable from how Crawla Cape seemingly was modified by CZ64 to have less lag as he mentions it on Crawla Cape's thread.
You can watch all the maps being explored in Riders 1.0 by following the playlist linked below, where you'll also likely notice the gameplay quirks.
The most noteworthy maps from this very first version would be Peach Castle, which actually survived virtually intact until the current SRB2Kart release as a hidden Map Hell map, becoming the oldest unchanged layout playable in the game, and Pipe Speedway, which is a very early version of what would later become Daytona Speedway, noticeable with the first half with the left circle turn and right turn with an earlier off-road shortcut to take with a mushroom/sneaker being already present, but otherwise being very plain in visual details and the rest of the layout.
Both Riders and the Mario Kart mode enjoyed a fair share of popularity back then, even in their primitive state, and aside from the aforementioned Violo and DaicheS9, there were a few other players such as Super Chris who made maps for Riders 1.0's Kart mode.
But the Mario Kart mode wouldn't REALLY take off until its next major update. See, in July 24th, 2009, SRB2 v2.0 was released, which added and polished many old details in the bae game, and was the logical step to continue SRB2Riders with.
It would take a few years until a port to the new version was finished in June 23, 2011, but aside from having the advantage of an improved base engine and new features to improve the Riders mode (such as the Riders countdown behaving like the original game, having to run through the finish line after the beam vanishes), the most noticeable change was that the Mario Kart mode was significantly reworked.