I'm using a 970pro on the back of my MSI Z270I and don't really have any thermal issues.
I do wonder if it's a possibility to run the ADT riser cable at the gpu side like @fabio did instead of running it at the mobo side. As the backplate of the GPU also tends to get hot. Don't know if this could harm the cable. It does have some spacing though.
This would give some offset between the m.2 ssd and the mobo backplate, allowing airflow.
I was initially thinking of putting a thermal pad between the m.2 ssd and the backplate and use the case as heatsink. Knowing how hot the case gets while gaming, I put that Idea aside.
I do wonder if it's a possibility to run the ADT riser cable at the gpu side like @fabio did instead of running it at the mobo side. As the backplate of the GPU also tends to get hot. Don't know if this could harm the cable. It does have some spacing though.
This would give some offset between the m.2 ssd and the mobo backplate, allowing airflow.
I was initially thinking of putting a thermal pad between the m.2 ssd and the backplate and use the case as heatsink. Knowing how hot the case gets while gaming, I put that Idea aside.