Some things make the route more difficult or less reliable to complete, and should be avoided when possible.
The on-reward-pickup voice line for Gemstones can have very surprising behavior. It’s very hard to control because it’s rolled using the RNG from combat (before reset) and if it causes extra increments or an unknown number of increments, it can cause the run to be lost.
Each RNG manipulation input required in a room increases the chance of a runner missing an input and falling off-route. Manipulations also take time, which makes the route slower. Even if the timer is paused, a slower route is less enjoyable to play and the runner can do fewer attempts because each attempt takes longer.
As a rough guideline, ForgottenKane and Vorime would try to keep each room to seven or fewer manip inputs in early access routing. With the advent of tools like the door prediction mod, it is very fast to try large numbers of increments and tempting to have high numbers of manips rather than backtracking. Try to avoid this temptation.
In Styx especially, the route requirements are very low so there are a lot of possible routes and finding one is relatively quick, so it’s worthwhile to optimize for fewer manips.
Most RNG manipulation in a route happens either a) right before doors unlock or b) right before you do the thing you want to manipulate (open a well, buy a boon, get a reward from Eurydice, etc). Runners will quickly get used to doing manipulations at these times. It’s possible to create routes that require manipulations at other times - for example, asking them to summon before picking up a boon or drinking from a fountain to put their summon voiceline on cooldown. The runner is more likely to forget this manip because of its odd timing, so if it bricks the run it can be especially frustrating. Sometimes this kind of oddly timed manip will be faster - as long as there is an alternate slow way to do the route, so that the run can be continued if the surprising manip is missed.
Losing a death defiance is slow. It reduces your health, which can make subsequent chaos gates trickier, and takes away High Confidence. It also affects the contents of Wells of Charon, since you aren’t offered Kiss of Styx in the first slot if you are at full DDs - generally, it’s better to assume the runner’s competence, and provide a backup strategy (if possible) if they take a DD rather than requiring it.
Losing a DD also ruins the aesthetic of a “run that goes perfectly”.
Rooms where you go directly to the exit without any RNG manipulation are fast, but require a lot of testing. Each RNG manipulation you add at the end of a room gives the runner some “buffer” to make changes in case something goes differently for them than for you. Many things will vary the voicelines played between different runners; unless you’ve tried these variations it’s possible to create a route that will only be possible in a very narrow set of circumstances.
In addition to being slower because there’s simply more distance to cross, large rooms also have more spawn points. This means they will have more possible spawn patterns, and more of a difference between fast and slow spawn patterns.
The amount of money you get in a route varies quite a lot from run to run. Routes tend to very money-intensive because you need to buy a lot of Light of Ixions at key points in order to stay on route. It’s tempting to route in buying rewards in shops at every opportunity, but buying unnecessary rewards can cause the runner to be short later on and brick an otherwise good run.
Routing in fixed sources of money such as from gold pots or room rewards can help a lot with this. Another common fixed source of money is to take a boon for the purpose of selling - just make sure that you’re actually offered the opportunity to sell it in the next midbiome.
The routed category is about the aesthetics of a well-planned and constructed route as well as about going fast. Make sure to get Epic boons. Make sure there is a reason for every reward you select.