easiest solution here is one of the conclusions your arrived at:
"Or should I just import the model with Appearances grouping and not worry about the updating?"
If you don't need to animate/move/live-update items, this is always the best approach. If you still need flexibility to live-update or animate, then supressing parts it probably the better way to go, but still be prepared for slightly longer save times and manipulation...especially if you have an enormous list of parts.
I created a new configuration and hid all the connector parts. Then I did a new project with Appearances grouping. Load time was about 4 minutes. (Almost instantaneous when compared with before!) Polygons 4,400,054. File size 56,912. Render time 3:57. But it was a pain when I wanted to load an updated model. I now had 2 models in my project and had to delete the first one. Then re-position the second one to where I had the original positioned.
I then did a new project but this time using Automatic loading. Load time was about the same, maybe even faster. Polygon same count. File size on slightly larger (57,274). Render time the same. Big bonus was the linkage to the original file.
1. Automatic loading is the way to go.
2. Keep file sizes small by setting up a "Visualize" configuration to HIDE all parts you won't be seeing in your render.
Thanks for your report. It helped me.
To re-import the model on an Automatic load setting, lock the camera view, make a new camera (or copy the first one), and make it active. Delete the old model (along with all imported appearances/decals) and import the new model into the second camera. Once imported, you can activate the original camera view and you won't have to reposition the model. I find that creating a new camera view also helps for applying appearances after setting up a view.