One thing I'ver noticed with 1000-part count builds is that sometimes the lag isn't from the part count, but instead parts and objects crammed together in one space. Take a look at a block which generates a sound barrier. It has tons of VTOL Nozzles crammed in one block. And this generates lag because of the sheer amount of parts.
I'm not saying the devs should do anything about it, I'm just pointing it out because it's a weird thing.
Different blocks are different lag heavy,
Obviously the standard block is light on lag
Wheels are incredibly heavy though
So vtol must be up there near the heavy amount