Golden Open Acrylics are an amazing line of acrylic paints that offer the acrylic painter a longer time to work with paint while it's wet. They are called "Open" which refers to the open time in which you have to manipulate the paint before it dries.
You can mix them with other acrylics but I wouldn't recommend it since the paint will dry faster. When I first used them I mixed them with regular acrylics and found myself in a frustrating middle-ground where the paint wasn't drying fast enough that I could start working on the next layer but not slow enough that I could continue blending.
My main "yay" moment was when I decided to use it for a very blended background of a dark and moody sky. It worked amazingly! I patiently waited until it was dry the next day to continue working on the piece. Check out the finished piece below:
When you use these paints you will notice that they stay wet on the palette much longer which allows you to really use up all of your paint before it dries. Since this might be a new situation for you I'd recommend keeping a few small canvases ready to paint on so that you can create a smaller work with any paint that is leftover.
In the summertime I have a hard time keeping the paint on my palette wet but you can diminish this problem by using Golden Open Acrylics. You can also try techniques of working wet on wet to create softer looking marks. You can use Golden Open Medium to extend the paint without decreasing the open time - other regular acrylic mediums will likely decrease the open time.
These interesting paints can give you a range of new methods without having to shift to another paint medium like oil or watercolour - huzzah!