So I had a 2x8 at 3600 but I can't buy that exact set anymore would it be fine to mix it would be team group on team group same speed but different ram.
It would probably work. There's a chance it might not. Sometimes RAM doesn't play nice together, especially if the RAM modules themselves are from a different manufacturer.
You could also buy the 2x16GB kit - assuming the pricing is such that it's cheaper per GB - and then add them to your system. In the end, you'd have 48GB of RAM if it works. And if it doesn't work, then you still get the 32GB of RAM you were originally planning on.