My best advice for RVZ is, quite plainly, to get better at SMK. Each and every track in SMK can be driven at or near Bowser's top speed all the way through-- even without NBT, on both NTSC and PAL-- with the possible exception of KB2. CI2 and KB1 are possible but much more difficult, though easier with NBT; you'll certainly need skill, yes, to do the VLs this way. If you're a neophyte, which I assume you are, then yes, the VLs will give you some trouble.
One useful tip I can give you for VL1 is to race against a CPU-controlled ghost who can clear out some ice blocks for you. But since this ghost is much slower than you, you will still have to deal with the ice blocks in lap 1, and you can clear out a couple to make it easier to do the snowslides. Press R to jump as you hit an ice block (or any other solid obstacle in SMK) to minimize speed loss. On PAL your first lap may be as slow as 13 seconds, but the rest of your laps can be 10"xx, allowing you to sail past the 1'00" barrier. The best players don't have to break any ice blocks, squeezing between them during the snowslide on every lap in order to save more than a second on the first lap by not breaking them-- but you're probably not one of them, if I'm not.

VL2 is definitely a track for advanced drivers-- it's in the Special Cup for good reason. If you can handle Bowser well, I'd recommend watching Leyla Hasso's 53"31 run. I used this as the basis for my own route on VL2 PAL, and it's a lot of fun to make all those jumps, but you have to be careful especially during the thread-the-needle part halfway through each lap (I'm sure everyone knows what I'm talking about). This will test your nerves, so don't get antsy in the final lap! You may not even come close to Leyla's PR (especially her current one) but just breaking the 1'00" barrier is a very good target for an intermediate-level player and will reward you with a pretty good rank, as a lot of players aren't good at VL2 (or VL1).
DP1 and DP2's long curves seem to be made for NTSC physics, but even on PAL it's quite possible to drift around the big 180s and come out with boosts by adjusting your drifting line-- start the drift a little later or a little farther out than you would on NTSC.
DP3
is tricky after the broken bridge. On NTSC you can get away with bouncing off the water to take a tighter line since you'll lose less speed than on PAL, but on PAL, you need to stay on the track, which requires a bit of tricky maneuvering on the left 180 immediately after the bridge, the zig zag part afterward, and then the right 180. Careful not to hit that wall (or the moles) on that right 180-- it's definitely the hardest part of the race for me.