It depends on what you mean by rendering. Vegas will use you GPU to speed up all video processing. Only two file encoders supported GPU acceleration. Mainconcept AVC and Sony AVC. MC AVC has always been hard coded to older GPUs and has never been updated for newer one. This has gone on for years and is unlikely to change. Mainconcept wrote it and they control it. Sony AVC does not seem tp support my 980 but even if it did, it would not get much gain in speed and never has over the years with the different GPUs I have owned.
So Vegas will/can run faster with your GPU for video effects/processing and such but it there is no hardware file encoder for AVC for the GPU you mention. Sony AVC does have Quicksync support for file encoding so that can be used if you set it up for that. Faster video processing speeds up playback/edit and file encoding (render as in Vegas speak).
I have a GTX 980 and VP13. No 14 as yet but there are no changes here.