That area definitely does chug a bit, largely because the lighting plugin I use, while great, is very poorly optimized, so I have to be careful with it. Combination of that and the size makes that area a bit chonky. It occurs to me that you only ever see one side or the other at one time (plus some stuff at the bottom), so I might be able to gain some by chopping it up, but that would be an enormous project. Ent. Dist II and II were originally one big map too, and when I had to chop those up it took...quite a while. And they have far less script events, and don't have an entire duplicate version of themselves for slut mode. So I'd be making, and testing, like three whole new maps.
For now though, I'll tell you what I've told others: the informal "Minimum Requirements" for GT are my own system: an ancient Ryzen 3. If your laptop's worse than that, I'm probably not going to put much dev time into optimizing for it, at least for now.