There are plug-ins that let you hear your mixes under the influences of what the streaming services ref level checking and adjustment might be doing.
https://www.nugenaudio.com/mastercheck-playout-loudness-and-dynamics-metering-aax-au-vst_41 For a track that is fairly even in level overall, the K system value is about 2 dB higher than the LUFS level. So a K 14 master is producing close to -16 LUFS. Aiming for a -14 LUFS master is similar to K-12. Which
Andy likes to master to. It is still important to know where
rms levels fit in and how they relate to LUFS levels. Working with VU levels right from the start will set up you nice for a great target LUFS master. I say dropping VU level reading is not good advice at all. If used wisely it can set you up for a great sounding mix. Nothing to stop you from using several measuring systems. I tend to work with VU rms for a lot of the production. It is actually easier and faster. Are you going to fiddle around with LUFS readings on tracks for example? I end up with perfectly balanced loudness wise tracks for an album using rms readings. Then in mastering you can bring in extra reading systems. e.g. LUFS and I also like checking on a dynamic range meter (DR) as well.
I work at the same level for all the mix production. That is either -14 or -20 for me. It is in mastering that I make the final change. I think in time it will be the norm for mastering levels to be much more sensible. I think -14 is an excellent level. It has a good balance of loudness , dynamics and transients.
The -23 LUFS ref level is also very versatile too. If you make -23 the constant level for a soundtrack for a film say, it means a whopping 23 of headroom is available if you needed it.
(They certainly achieved it in Blade Runner 2049!) It is also very close to K-20.
The thing that makes LUFS interesting is the time over which the reading is taken. It tells you a lot more about the overall level of something. Over much greater time. VU rms is still longer and slower than peak values but over much less time than LUFS. They are all relevant here. Peak reading, rms reading and now LUFS reading. We need them all.