Hi Raul
So, I played around with Oxygen and Toolset together, using a default Oxygen install with the atomic site template.
As you will know, Oxygen doesn't use your theme at all (it doesn't even load the functions.php file), and doesn't use the theme templates such as single.php.
That means you are not going to be able to create Views Content Templates to design your single posts in the same way as you can with other page builders.
However, I found that the template Oxygen uses for single posts which includes the post body seems to run the_content filter before outputting that content.
What that means is that you can still create Views Content Templates for single custom posts, and when you use Oxygen to create a template for that post type, the content area of the page is still replaced by the Views Content Template, much like it would be in a regular theme.
So the Content Template can output your custom fields, as required.
However, I also checked to see whether it would be possible to insert custom fields in other areas of the site, and it appears not.
The text (and rich text) modules do not parse shortcodes, so you couldn't copy and paste in a Views shortcode or Types shortcode.
But you can place WordPress widgets arbitrarily in your pages and templates designed with Oxygen, so you can add a text widget and use shortcodes within it (but you will need to enter them manually, there is no Fields and Views button to insert them).
Likewise you can use Toolset's WP Views widget to insert a View.
You can also use Oxygen's custom field module inside the WordPress > Dynamic Data section (recall that Types fields are stored with a 'wpcf-' prefix.
So, in sum, without any formal integration it looks like you can already do quite a lot with Oxygen 2 and Toolset together.
I'll raise this with my colleagues to see if we might add more options for inserting Types fields. I also haven't tested this with other Toolset plugins than Types and Views, I expect there may be issues with things like edit Forms, for example.