Writing in-depth reviews of modded racetracks in racing games isn't something I do very often, so I hope that you bear with me as I post my observations and thoughts on your tracks. For this review, I'll be categorizing my thoughts in three ways: the standard observations and thoughts, elements of tracks that I strongly suggest you change, and notes about tracks which may be contentious among players, in this exact order. As it is, I'm ranking tracks based on how they would be perceived as natural extensions of the base game, and most importantly whether or not they would be fun for people to play in netgames, but I'll do my best to be fair to tracks that are looking to break out of this mold as well.
P.S.: I'll only be ranking racetracks here (for the most part), battle stages and special stages are outside of my area of expertise! Sorry!
So, my thoughts on the Epic Cup Revival:
Wow.
Your original Epic Cup pack for SRB2Kart already had amassed popularity of its own with your clean and unique track designs. But, truth be told... I never actually liked your pack. I'm generally picky about track packs to begin with, but the combination of the stale SRB2 2.1-esque visuals and track designs that didn't really excite just made your pack not something I ever really thought about, outside of you trying something really weird like in Ante Station. So it legitimately impresses me that all of that is gone now. Now I really do think Twins' Epic Cup is epic.
It's certainly not just the fact it's an entirely new game with a more robust and complex set of mechanics, either. All the tracks in the pack are virtually unrecognizable from their SRB2Kart incarnations, all with changes that I deem to be for the better. Layouts are refined and made more exciting with more complex and polarizing terrain, track visuals are made even prettier as old SRB2 stylistic conventions are foregone, and the implementation of Ring Racers' brand new track elements allows the tracks to shine even brighter and present unique identities in their track design.
There's love put into this track pack and at only 3 tracks in out of a planned 5 (6? idk) I can't wait to see what else you cook with it.
That does it for the overall summary of the review. Here are my write-ups on each of the tracks in the pack:

Aqua Paradise Zone
This is such a glowup. The original version of the track was my least favorite in SRB2Kart: I didn't like the visuals and the track itself wasn't anything to write home about. ...I should probably stop hating now.
But seriously, the track went from 1 to 11 in terms of track design. Apparently basing it off of an SRB2 map (that you made) was an inspired choice; the layout now has interesting eccentricities and gists to it. There's plenty of elevation changes and unique sloped terrain and there's even an underwater section! The track also looks prettier in this game, though I'm not sure what exactly changed other than the new lighting system. Nevertheless, the track is really enjoyable now which makes me glad.
Recommended changes:
* It's actually kind of hard to see the water spout that's right after the trick panel near the end of the track. The similar gimmick in Blizzard Peaks is in an area where the whirlwinds have the highest visual contrast to the "background", so a similar thing would be welcome here as well. Sorry that I'm asking you to redesign this portion yet again.
Things to consider:
* The track practically ends after the underwater section, as what follows is an incredibly short portion of track followed by an automated segment. I've already mentioned a similar problem in my review for Begine9's Coins Cup for the Chemical Plant Zone track, where I think it's rather awkward to end the track immediately with an automated section as players will otherwise expect that there's just a little bit more track to race and do battle on. All base game tracks that have an automated section right before the end actually dedicate a small portion of track for after said automated segment, such as Launch Base Zone.
* The frequency of item boxes per row is rather high, allowing for the most amount of potential new items per player. Granted, most of the item row placements are in wide portions of tracks, so it's natural to have a high amount of item boxes.
* You can overshoot the trick ramp at the end of the underwater section and go over the dash panels. Really annoying, but you're free to chalk this up to a skill issue at the cost of... well, people getting annoyed that's a skill issue.
* You can get the best speed boost from the trick ramp before the water spout by tricking *after* you reach the water spout. And to do this, all you need to do is mash the trick button until you're out of the spout.

Ante Station Zone
where did the hyphen go
It's really strange and unfortunate that the main gimmick of this track, and the level it's based on, had to be excised entirely from Ring Racers because it doesn't work for a non-negligible amount of people. Fortunately, the rest of the track more than makes up for it, with a fun layout full of interesting setpieces and brand new vibrant aesthetics that look a little less like SRB2 2.1. We will still mourn the loss of that one wack portal shortcut, though.
Recommended changes:
* None.
Things to consider:
* For most rows of item boxes there's one item box that's perhaps too many, at least going off of how base game tracks are designed.
* Putting the last set of item boxes in the middle of an automated section, especially one that people can't see ahead of, is rather rough. Especially since there's less item boxes in said row than in most other rows in the track. On the other hand, ring boxes in the section after the item boxes appear to be particularly powerful, so I suppose this works as a counter-measure.
* A last section where you have to do a sort of inverted slalom where you do turns while going uphill is probably unpopular with people.

Heaven Pass Zone
This is my favorite track in the pack so far. It's a really really fun take on Heaven Pass, both in SRB2Kart and its original incarnation in SRB2. The slopes are really fun to go down on and so is the trick pad section, and it's visually wonderful to boot.
Things to consider:
* The bumper during position is good.
* The encore mode aesthetics for this track are kind of lame, if you ask me. I would more or less, at the very least, prefer it do something like turn into dawn for like the final lap only, instead of the track being the exact same except at nighttime only. pretty unimportant point anyway
OTHER:

Entryway
I like this one. I do think just the original Running From Evil should play in here still, as an alt song. And perhaps without the fucked up playback holy shit dude