Running into VRAM limits (5.2/6GB VRAM), and parts of the preview start to look a little wire-diagram-like. How can I temporarily lower graphical settings so that the lag is reduced? Also, will importing it to Visualise get rid of the wire-like diagrams affecting some portions of the model?
There are a few ways to save on memory.
1) Can try creating sub-assemblies and saving them as a part (e.g. the turrets)
2) Can also try Large Design Review mode (I have embedded the video here. To activate it go to the 1:11 mark)
Option no.2 is very effective in dealing with huge amounts of parts and is designed to help laptop GPUs.
Regarding getting rid of the wire-like diagrams thingy, it should disappear after you click render.