To which value should I normalize my audio files?

[EdgarRothermich]

.. or the coolness factor of a dancing needle" (where do you even get such silly imagery from?!)

Not my quote. It was mentioned in one of the responses.

The posts here are meant for answering the OP questions.

Yes, but often the answer is not as simples "do this" or "press that". Sometimes it is necessary to provide a little more context because it is often unknown how much the OP knows already.

Everyone's entitled to their own opinion

You forgot to finish that sentence
You are entitled to your own opinion, but not to your own facts.

it's up to the OP to decide which piece of info he wants to absorb or try out but you seem to be picking on everyone every time the term "VU" is mentioned by quoting them and insisting that your answer is definitely the right one.

Again, I'm not posting opinions, I'm posting facts. Don't shoot the messenger. Everybody can read up on VU Meters, their specs, etc.

With due respect, I have no interest in anyone who poses as an audio guru on YT, that is until you decided to quote me.

Another dangerous meme on the Internet (or society in general). I don't come here and say, I'm a guru and I'm a right and you are wrong. It just happens that I work in audio production professionally for over 30 years and I teach audio courses at the University. I just know a thing or two about that subject and I'm happy to share and discuss.
What I'm seeing more and more on the Internet is that a lot of wrong technical information is spread around and picked up by beginners and I just try to enter some facts here and there.
Unfortunately, people who know things or the field of science are demonized lately, which is a little bit worrisome (disclaimer, this is my opinion).

I suggest you keep your biases to yourself instead of continuing to trash on other user's posts and hijacking the OP's thread or bombarding the OP with a whole bunch of info that he wasn't even asking for further confusing him.

Again, posting facts is considered "biased". Correcting information is considered "trashing". Providing additional (hopefully useful) information is considered "bombarding with a whole bunch of info". Just wow.

It seems that you don't even understand that VU meters are for observing how hot a signal is (on the long term, or aka average) relative to the circuitry of an analog (or analog modelled) audio processor which is directly related to OP's 2nd question. VU meters were never meant for loudness measurements. In the old days they will use RMS or PPM meters for that instead.

It is interesting to suggest that I don't understand VU Meters and then continue to state so much wrong/questionable things about VU Meters that I don't even have the time to correct them.

I think you're falling on your own point here already by denying the OP a chance to learn about VU meters plugins,

Again, I don't know where that is coming from. Giving advice to the OP that a VU Meter is the wrong tool (based on all the facts that I provided) doesn't "deny" anything. That is just weird.

[sambaji]

I am no expert, but if I was to normalize my audio files as part of the gain staging process for mixing, I would shoot for an RMS average of -18 dBFS with peaks hitting no higher than -10 dBFS. I think most software normalizes to true peak value. If that's the case I would choose -10dfs peak, or -12dBFS, as you mentioned. Basically, I would shoot for a level that people generally recommend for gain staging. However, instead of normalizing each audio file, I usually insert a trim plugin on each channel (or adjust the track gain directly) to get my starting track level (-18 dBFS RMS) using a VU meter (0 VU = -18 dBFS). -18 dBFS (O VU) is a good level to start with if you plan to use plugins emulating analog hardware, which traditionally used VU metering. That's why I use VU/dBFS RMS metering, not LUFs, for basic gain staging. LUFs metering is something I would use at the end of the mix bus chain or for mastering to get the right level for streaming. Some "analog" plugins come with trim adjustment and VU plugin built-in, in which case you can forgo the VU meter plugin. Also, if you DAW displays both RMS and True Peak for each channel, you can use that instead of a VU meter for initial gain staging. For a good overview on gain staging (includes a video), check out https://www.musicianonamission.com/gain-staging/

A great free VU meter vst is https://www.tbproaudio.de/products/mvmeter2
For a more modern loudness meter (e.g., LUFs), check out https://youlean.co/youlean-loudness-meter/

Featured snippet from the web
"DBFS is dB Full Scale which refers to digital full-scale readings. Zero is the top of the scale and it can not be exceeded. RMS is Root Mean Squared and refers to the average level, not the peaks which can be much more than the average level. The -18 dB is the dBFS reading of the VU equivalent."