I will be quick.

What is the best:

·Using the sample rate natively in the host? For example 88.2 Khz
·Or using an oversample effect x2 (external or built-in on the synth) but the host running at 44.1 Khz? (Which would be 88.2 Khz)

Is it the same?
What do you think is the best way?

Yes, i know all the stuff about making tracks at X samplerate quality and about what is able to perceive the human ears, etc.
But i want to know if this is EXACTLY the same, and what is the best way in case they are not the same, etc. Just that doubt.

At the moment i'm using 48,0 Khz, but maybe i will use a higher sample rate soon.

That's it. Have a good day

I can't answer to all your questions but I try my best because nobody has answered to you yet.

Running your projects with x 2 samplerate is pretty much the same thing as 2 x oversampling. Except that oversampling needs an antialias filter that can make things worse sometimes.
Studio 1 for example has an equalizer that has a "high quality" button.
I know it's supposed to make things better but IMO it makes them worse. When it's engaged it's cutting high so much that even I can notice it.
I remember some developer saying that oversampling is not a perfect solution but a compromise.
Oversampling can have artifacts if it's poorly designed. It's something to keep in mind. I personally hate aliasing but I don't like to have a filter that I can hear on the signal path either.

I did some unscientific tests sometime ago and I ended up choosing 96khz for all of my projects. This way I don't need oversampling that much. I "feel" like it's made things better. It could be a placebo though

One good thing about oversampling is that you can use it on places where it has most benefits like distortion etc.
This can save lots of cpu when you compare it to running everything in higher samplerates.

I suggest that you do some tests to help you make a decision of whether you should raise the samplerate or not.

Here is an excellent, very well explained and detailed article that can help you with this:

http://www.tweakheadz.com/16_vs_24_bit_audio.htm