The following is intended to act as a routing guide for the Any% (No Memory Maniuplation) category, with the major most examples of relevant data I can think of.

Let's begin at the most obvious starting point: the absolute fastest route.

TAS Route

Polar Panic - Gem, Crystal Pogo Painter - Gem Jungle Bash - Gem, Crystal Tilt Panic - Gem, Crystal Pogo-A-Gogo - Gem Space Bash - Gem, Crystal Desert Fox - Gem, Crystal Melt Panic - Gem, Crystal Snow Bash - Gem, Crystal Metal Fox - Gem, Crystal Dot Dash - Gem, Crystal Manic Panic - Gem, Crystal Drain Bash - Gem, Crystal Jungle Fox - Gem, Crystal Ring Ding - Gem

I tell a lie here as the true TAS route would do Toxic Dash gem in favour of Pogo-A-Gogo gem, due to lap skips. However I decided to not count that as it's a real time irrelevant anomaly. Additionally, in a real time situation you're far more likely to do Toxic Dash gem faster than Pogo-A-Gogo gem. So that would be the "RTA Optimal Route". I doubt I have to note how absurdly inhospitable said route is, but that's it if you wanna go for gold.

So from that knowledge let's take a look at the next step down, the route(s) used by "top" runners.

Consensus amongst the large majority of runners is that Manic Panic and Drain Bash gems are particularly troublesome. Their location in Warp 4 makes them annoying to go for as they can both easily trash a run, and this would be over an hour and twenty minutes into a run. Crystal-wise, Metal Fox and Drain Bash are the two longest, and can both cause trouble. Drain Bash particularly features an issue where one of your power-up attacks hitting an item crate results in your health being reduced to one hit remaining. Melt Panic crystal can also cause problems due to the nature of the challenge, aggressive or stupid AI can easily kill you.

So, what can be done? Replacing them, of course!

El Pogo Loco - Gem Toxic Dash - Gem, Crystal

Unfortunately, at the "sub 2" route level there's not much room for movement. It'll mostly come down to your personal preferences as to what is substituted. Toxic Dash gem is a very good choice and you're unlikely to see a route that doesn't do it. El Pogo Loco gem, however, is not an "easy" item and costs a lot to fail. Some runners still find it preferable to Manic Panic or Drain Bash. Toxic Dash crystal is a solid replacement for either Metal Fox or Drain Bash, as on average it'll be a similar length but less problematic than either.

Finally, we have the low tier route choices, looking mostly to remove as much of the worst as possible.

Crashball - Gem Pogo Painter - Crystal

Crashball gem is significantly slower than any other gem in the route is likely to be on a first try basis. However it's easy and right at the beginning of the game. Pogo Painter WILL take you 2 minutes, due obviously to the timer. Again, like Crashball gem, it's very easy and at the start. Including Toxic Dash crystal, only if you really can't do one of Metal Fox or Drain Bash crystals should you consider this.

Therefore the "safest" route would look like:

"Safest Route"

Crashball - Gem Polar Panic - Gem, Crystal Pogo Painter - Gem, Crystal Jungle Bash - Gem, Crystal Tilt Panic - Gem, Crystal Pogo-A-Gogo - Gem Space Bash - Gem, Crystal Desert Fox - Gem, Crystal Melt Panic - Gem, Crystal Snow Bash - Gem, Crystal Metal Fox - Gem Dot Dash - Gem, Crystal Manic Panic - Crystal Jungle Fox - Gem, Crystal Toxic Dash - Gem, Crystal Ring Ding - Gem

Or with Melt Panic crystal replaced with one of Metal Fox or Drain Bash. I must reiterate that it really is down to your preferences/experiences as to what your personal route should look like. It's entirely possible to sub 2 using the safe route.

So there you go, hope runners find some use out of the information here. However I must remind you that the true most intelligent play in Crash Bash speedrunning is to not speedrun Crash Bash.