Wanted to provide an update on my issue. I noticed GPU sag when putting the rig back together and, having propped it up temporarily to ensure it was level, the issue seemed to completely disappear (extensive stress testing and game play - not a single reoccurence since 12 DEC) all settings I had in place are now all higher as a result seeing the 2070s can perform well.
I had been using the arm mount which came with the GPU, however wasn't secure enough it seems. Have since bought a GPU Stand and everything is ship shape and shiny. I would assume this means there is a lose connection on the board or connection on the GPU PCIE (?).
Plan to switch out the board this week once my new GPU arrives and can put this all to bed. My 2070s will be going to a family member and be giving them the stand to make sure they dont experience the same issue as I did.
Thanks all for your input, suggestions and helping educating me along the way!