Diving into balanced

Go with the longer cable. It's much easier to manage.

Balanced cables are used in professional recording because a balanced connection is much better at rejecting noise for long runs. It's not unusual to have cable runs that are 50 feet or more in a studio and even longer for live music. Professional gear doesn't have RCA connectors. Nobody would use them.

Balanced architecture in an audio component is more expensive to implement. I have vintage Krell components with balanced connections and I do run balanced cables on them. However, I only have two balanced inputs on my preamp and I have several sources with balanced outputs. I have compared single ended RCA cables (Blue Jeans) with balanced cables on a few different components into the preamp and I can't hear the difference. But my amp is a different story.

I have a Krell KSA 300S amp that has balanced inputs as well as single ended inputs. I have tried both (you need shorting plugs in the balanced inputs if you run single ended cables) and there is clearly a difference in this application. The single ended option is much noisier. I found this when I sent my preamp in to be recapped (I hooked up a different preamp that only has RCA connectors) and upon further investigation I learned that Krell does not recommend using the single ended connections on this amp. Interestingly, the new D'Agostino amps do not even include single ended connectors.

My opinion is that if you have equipment that has balanced connectors then you should use balanced cables whenever possible. The manufacturer spent extra money on this feature so you might as well use it. But I think you would be challenged to hear a difference between a source component and your preamp.

Balanced IMO is considerably better in my system. Granted I have a long run preamp to amps. Consider this: if balanced isn’t necessarily better why do companies provide the option knowing the unit will be more costly than single ended? Just another up sell?

Common mode noise rejection is no joke. 6db quieter compounded with each component (the next component has received and pushes out an even lower noise level and so on).This can be significant. The connections are more dependable and components can be placed with more latitude.

Mentioned above as being better in my system. Having a considerable sum invested in my system, until going balanced I sensed something missing (the rabbit hole is in play here), afterward a sense of completeness. Good luck. JMO

To me the decision is also dependent on what sources you have in your system, and if they are providing balanced connections or not.

For example my Moon 310 LP phono stage provides 6db more s/n ratio using a balanced connection to the preamp than if I use a single-ended connection.

To me, that is significant given that it’s upstream (close to my turntable source), so it made all sense in the world for me to use a balanced XLR connection, and then it felt natural go for the same between the preamp to the amp (and from the streamer/DAC to the preamp).

Also, with separates and a large number of power cables that by necessity- at least in my case - runs from each separate and it essentially practically impossible to keep away from the interconnects, balanced interconnects feels like the right way to go.

For me, that is.

There’s no definitive answer. Typically with balanced components you will get lower noise floor using balanced cables. The XLR output is usually higher than SE. using matching preamp and amp helps with synergy. If you use different brand preamp check to make sure the output gain and impedance match well with your amp. 
And +1 on 1m length. I actually have a 2m set going into the amp - gives me more flexibility. 

Definitely 1 meter or longer. You never know what your arrangement will be later. My preamp and power amps are 7.5 meters apart. Nice to have sources close to the sitting position and the amps close to the speakers. Speaker connections are short with this arrangement. XLR is ideal for long runs.