Can you create groups or folders?

Maybe - if the model is in one folder is there a way to split it up?

Select the part you want to put into a folder, then press J to put them into a group. You can then hide the group by pressing H, then press Alt and H to show it, or you can click the eye icon next to the group name in the panel on the right.

Thank you!

You can also use flat shading in the viewport options. It is not as pretty but much easier and faster to compute. If you still want to use the normal shading mode you can set the details to low.

Thanks all - just to circle back, it looks like hiding has minimal impact on speed. I wish there was a way to "unload" groups, which may be the only way to fix this issue. I've reduced the shading, but also not a huge impact. I appreciate the feedback!

Hidding shall have a biggest impact if it doesn't there is something not right. Elements are in memory (CPU and GPU) but outside of the rendering pipeline. Also make sure that you hide the edges. This feature basically doubles the number of objects.