I use Reaper DAW too, so +1 for that and it has a free version.
I also have sibilance issues (which is why I am on here looking to see what the solution is for ‘Jun’ when set to breathy it gets real bad), but Toneboosters has a good free Sibilance VST plugin which is actually sometimes better than the paid ones I also have (Waves de-esser and another).
To be clear, Reaper does not have a free version. It has a 60-day trial, and does not prevent you from using it after the trial period.
Using an expired trial is not the same as using free software.
I use Logic Pro X, and izotope’s Nectar 3+, before that i used Logics own plugins and sometimes Toontracks ez mix 2… But it is so much easier now 
…i might soon upgrade to nectar 4
I’m using FL Studio 20.
The usual vocal chain I use is just Reverb, Saturation, compression, and thats it. I use that all the time its always works no matter which voice I use, because the saturation did most of the job on shaping the tone and putting where it sits on the mix. No I dont uses fancy plugins I’m gonna list the plugins I use.
But overall just treat it like how you mix a real singer would be.
There is no correct order to mix a vocal, you can do it anyway you want, each mixing engineer have their own preffered vocal chain and plugins of their choice.
I recommend you to watch a few tutorial on the fundamentals on what this does and what that does. Then just mess around with it and have fun. If that doesnt work dont keep throwing things into it, try again tomorrow with a fresh head. Remember it doesnt matter if it sounds good then it works, good luck!
One trick that’s neat is to put a stereo compressor on the music only bus and send the lead vocals to it’s sidechain so it ducks the music when the vocals are singing. Not too much now, just a couple dbs of gain reduction to create a sence of pressure.
one trick if using the FabFilter EQ to match to the instrument track, then invert a db or two on the instrument track w/ the dynamic setting to allow you to lower the vocal into the instrument track a bit more without having to duck the entire track only the vocal frequencies. probably can do this with other EQ as well like Waves F6 etc but the FF EQ imho is super easy.
I spent an awful time mixing my first songs that use Synth V and what improved the sound the most for me is vocal riding. I used GainAim plugin.
I find it makes the vocals smoother. When layering multiple voice tracks, using vocal riding on each track makes the sound more consistent, more that what I could achieve with compressors.
Also, some tools some tools like Focusrite FAST plugins give a good start to EQ and compress using AI. What I like with the FAST EQ is that it gives meaningful settings, such as “Body” “Nasal”, “Sibilance” to tweak the sound. I am not a sound engineer that can use Pro Q effeciently to dynamically cut a frequency based on a sidechained track. Tools like Focusrite Fast helped me.