So, Some months ago I bought a Razer Kraken Pro for 72€ , and in order for it to work with 7.1 surround I had to install synapse and get "razer surround pro" (I had a product key for free in the headset's box).
Basically was using synapse only for my headset, and it's working as it should.

The only issue I had is that it asked me for update each time I started my computer. And it also recommended me to install synapse for my Razer Abyssus 2014.

Only recently (tonight to be more exact :)) I finally decided to update my razer synapse and install it for my abyssus 2014.

And guess what ? They fixed the 1000hz polling rate tracking issues. \o/ Now that I have the latest synapse version and set my abyssus 2014 to 1000hz, I can finally do very fast 360° turns in-game without ending up at 210° 2 out of 5 times. Basically now every flick 360° turns are perfectly accurate, just like when I used my abyssus at 1800dpi 500hz plug&play without synapse.
And the mouse tracking at 1000hz is now just as good as at 500hz, it feels very consistent just like with the old abyssus :)

So, starting from now on, I will keep using synapse and 1800dpi 1000hz (instead of 500hz previously). Ofc it doesn't make a significant difference but it's more placebo/psychological than anything. And it's good to play with the exact same settings than with the old abyssus :).

1800dpi 1000hz for life! :)