Game in editor keeps lagging

I have a landscape with the maximum size settings ( component size and maximum kilometers ) , I have a couple of cities aka buildings in my level places that hold vertices above 100,000.

I have all of the props and buildings have distance LOD’s that shrink the vertices down to just 34 each building and also cast shadows disabled on LOD’s

I checked all the Optimization performance tools, the majority said ShadowBuffer so like I said i disabled shadows on LOD

When I hit play the whole game drops to 2 or 3 FPS then very very slowly adjusts to 20 then 30 then 40 FPS why does this happen?

Hard to say what is causing this without a little more information.

What are the specs of your PC, and what exactly do you mean by maximum size settings of the landscape?

The last one most importantly, because as far as I am aware there is no maximum. Only maximum single tile size.
So by maximum size, I assume you mean “8129x8129”. Which if its at 100% scale will but just past 8km in X and Y.

I imagine the issue of lag is caused by the landscape size. Even on a beefy computer 8129x8129 can drag a bit. Have you considered using world composition so that the landscape can be loaded in in chunks?

So I have two machines -

first PC - Processor : AMD fx 8370, GPU : GTX 1050 ti 2GB, RAM : 8 GB

Second PC - Processor : AMD RYZEN 1600, GPU : GTX 1050 ti 4GB, RAM : 16 GB

By “maximum size” I mean the maximum component size of landscape that UE4 offers + Fill world button

Using the maximum component size isn’t always great idea. I suggest you have a read through this if you haven’t already.

Also, other than the CPU in the second one, neither of those PC specs are that beefy. I assume they are budget PC builds due to the low end GPU? Which also leads me to believe they are running HDDs as opposed to SSD’s?

I would have a look at some existing example projects on the launcher. Particularly the landscape related ones. See if you get the same sort of issues. But I am doubtful of you getting decent editor performance with those specs.

I am using SSDs on both the PC’s I have UE4 installed on them but the OS runs from the HDD

also I cannot use world composition because it asks me to copy my landscape 3 4 times then load that in chunks so its not acceptable

I would look into using world composition if I were you.
Splitting the landscape will make things much more efficient.

In the landscape editor, you can select tiles and send them to a new level. No copying involved.
Try it on a new map without anything else in the world so its faster and not going to break your existing map.

Ok ill give this one a shot