I have been doing some research, and I have come to this conclusion
I WOULD LIKE YOU TO KNOW THIS EXPERIMENT IS DONE ON A POTATO WITH 18 MONTH OLD GRAPHIC DRIVERS.
Grid size:
I made a local mod that made the grid size 20000 by 20000, the game takes 3 minutes to load (bare in mind my PC is really bad and I had abh mod on too) and around 30 secs to load in a new galaxy, to continue a game doesn't take as long to stabilize after those 30 secs.
Ship size:
A ships size can affect game play majorly, something like the BSF seraphim takes around 30 seconds to load in the ship to place it in the game, Cosmoteer may go unresponsive for 10 secs and then it can run fairly OK at 10 FPS,
AI/Weaponry:
Going off of the seraphim experiment, if you turn AI on, it will cause a lag spike, especially if you have multiple ships, then it will return to a normal "silky smooth" 10 FPS, 1 small ship firing while you are watching can cause a crash within 10-20 seconds, after you watch the program go unresponsive for a minute or so. (It took up so much memory that it crashed OBS and sent chrome unresponsive for 30 secs)
Explosions
May be the main reason for the drop from a "silky smooth" 10 fps to 0.0000000001 fps and then a crash
Crew:
The crew may be another problem, I'm building a big ship now and it has a crew of 600 (ATM) and it can cause random drops in FPS that may cause a crash or make you restart your game (usually the drop of frames last a minute or so and are pretty rare) This brings the FPS to 3 so yeah 600 moving entities is a lot to handle at once.
This can be easily solved by turning off the view for the interior ship, however if you do this while it is lagging the shift from the interior to the exterior will cause a crash.
Slow Motion:
Slow motion is believed to stop lag however I have seen that sometimes 1/2 will lag less than 1/4 or 2x would lag less than 1/4x, it depends on the situation
How to stop lag or crashes?
This may sound strange but if you look away from a fight with two big ships it will not lag nearly as much, and if you pause the game every time the screen freezes you have a chance to avoid a crash.
I hope this has helped you understand the limit of your potato (or god) with lets hope better graphic drivers.