In a search for a better sound - Q&A

The sound you are looking for is usually achieved in several steps.  First of all, microphone model & vocalist match is the most important step: some mics may produce a harsh sound with one person and a smooth one with another.  Another step is clever mixing.  Any harshness you can hear in dry vocal takes can be hidden by using de-essing, reverb, and equalization.

Voxformer is a good plug-in tool that will definitely help you produce a better vocal sound.

Another option is to use Peakbuster with its M3 smoothing mode - it usually reduces vocal harshness without affecting vocal's tone and clarity.

This is usually achieved by various levels of harmonic distortion since distortion (overdrive) "crowds" the spectrum with a lot of additional spectral components.  For such approach you may try VariSaturator.  Another approach to getting a fuller sound is to add synthesized spectral components: LF Max Punch can be a good solution here since it features a sub-harmonic frequency synthesizer, its "Fuller Bass Guitar" preset can be used as a starting point (for clean guitars you may need to raise up crossover's frequency a bit).  Another widely-used option is to apply a slight chorus effect: Water Chorus can be used for this purpose.

Multi-band compressor can lower spectral dips and notches by means of reducing dynamic range at specific frequencies: when it reduces a dip, this also reduces a nearby notch in the spectrum.  It performs two tasks at once--compression and spectral re-balancing--and does this dynamically.  Static EQing may not always succeed since it applies a static EQ response which may be good on average, but in some places in the track may still sound a bit hollow.

So, if you have plenty of dynamic range left after mixing session, Soniformer multi-band compressor won't usually hurt: with it you may achieve a desirable sound "gluing" and at the same time remove audible dips and notches, without much effort overall.

Both are suitable for subtle harmonic enhancement processing.  Both Warmifier and HarmoniEQ can be used to process whole mixes and individual instruments.

It's a "dilemma"-like question.  EQ after compressor adjusts compressor's achieved dynamics, while compressor after EQ adjusts EQ's attained frequency balance a bit.  If you need a strict peak level control then always use compression after EQ.  If frequency balance or "clarity" is more important then use EQ after compression.

You may use Soniformer to manually match the stereo width of the tracks by first looking at the correlation meterings of the target track and then trying to achieve a similar metering in the source track.  However, if there is no stereo information in the source track available you can't usually do anything positive unless you add it with some sort of reverb first.

Overall, this may be a tough task to accomplish.  Indeed, compression is close to be the only solution to this problem.  However, in order to get more precise results you could try Soniformer for this task since it allows you to apply compression to a narrow range of frequencies.

Or you may try Voxformer's De-esser tuned to frequencies where vocals are present the most.

It is almost impossible to transform and match vocal timbres - not only different timbres like male to female, but also minor timbre differences due to changes of a person's state of mood.  Because the vocal tract is very "non-linear", mathematically speaking.

You may try matching the EQ shape of two voice recordings: this usually helps to get rid of microphone proximity differences.  For this you can use CurveEQ.  But completely matching two different timbres with all their non-linearities and harmonics may be impossible to implement.

It is suggested that you try Warmifier and VariSaturator as the most suitable saturators for full mixes.  Multi-band saturation offered in Drumformer is also worth a try.

As most Voxengo plug-ins feature an output level meter with the “out/in” indicator (input-to-output loudness difference), adding an EQ auto-gain compensation (or auto-gain on any other stage) is unnecessary: it is enough to click on the “out/in” value to match the output loudness to the input loudness.

All saturators "glue" a mix together to some degree.  You can try Warmifier and HarmoniEQ, its LT module — these are the most "invisible" saturators.