Obviously there are cheaper solutions, but these are high quality/performance, I hear no degradation of the signal using them and preserves the advantages of using balanced cables. These also have the option of 1:1 or 1:2 signal gain if needed.
To answer your other question: if you float a signal pin, it's no longer a balanced cable and you lose 1/2 of the signal strength. There is no point in using the XLR out on the source if you're going to do that. Same is true if you use RCA out of a pre-amp to XLR in on an amp. You then also have to keep the ground pin connected on both ends to provide the return signal path, inviting ground loops. That's one nice advantage true XLR provides, you can lift the ground on one end of the cable if needed. Sonically I can't imagine using one side of a balanced signal is a good idea either, but never personally tried it.
Actually if the balanced source is AES48 compliant, the output level is exactly the same if it is operated balanced or single-ended. An output transformer of a balanced device is likely the easiest way to understand this. If its balanced, its secondary is tied to pins 2 and 3 of the XLR and nothing else (pin 1 is chassis). If you tied pin 3 to pin1, you can see that the output Voltage will stay exactly the same.
Its the same way with a phono cartridge, which is also a balanced source. Its output will not double if you run it balanced.
If the output running balanced is twice that of single-ended, its a sign the source is not AES48 (one of the balanced line standards) compliant. Instead its merely two single-ended outputs that are out of phase with each other. Use one you have 1X output level, use both you have 2X output level. The problem is it references ground:
Another reason to avoid 10’ RCA runs is that the weight of the cables will always be pulling on the connections. Friction fit is usually fine for short cables but I have had problems with this before. Granted, these were pretty cheap cables but I had a 6’ set of RCAs that gradually slid out of the jack. Was causing really weird problems and was only able to figure it out when it came out completely. High quality RCA cables tend to be heavier than than regular ones and so work against themselves a bit.
All of this is another reason XLR connections are used in pro and studio environments. It might be a little overkill for home use but it sure does feel good to have the XLR click into place.
There are three main reasons to use balanced connections in the studio or at home:
1) ground loop immunity, since ground is ignored in the connection (unless the equipment is not supporting AES48)
2) immunity to interconnect cable coloration, since the shield is not part of the audio connection
3) lower noise due to Common Mode Rejection Ratio (CMRR) where if a signal is imposed on both conductors in the audio cable, it will be rejected by however many dB of rejection is available to the system. Transformers often offer about 100-110 dB of CMRR.
It is worth doing this in tube equipment! Tubes are more sensitive to speaker cables so its handy to keep the amps as close to the speakers as possible, so as to minimize speaker cable length. This way you get more resolution and better bass impact. The problem is then the long interconnects that might result. But if you have a proper balanced connection, you can run really long interconnect cables without much cost or coloration. I use 35 foot cables in my system at home, using Mogami Neglex, which is not an expensive cable, but one which, if used properly, will sound as good as cable that might cost $1000/foot. I'm not be hyperbolic; I've done such comparisons in the past. I've been running a fully balanced (all tube) system in my home since 1989.
