1. empty database (1 Foundation, 1 Wall, 1 Ceiling): ~574 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2448625328
   
2. 2500 Foundations (50x50 grid): ~541 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2448626054
   
3. 2500 Ceilings (50x50 grid): ~540 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2448626466
   
4. 2500 Ceilings + 5000 Walls (50x50 grid): ~457 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2448633887

summary: funcom optimized the building system well enough. there is no difference in performance between foundations and ceilings.
in fact it is a bad thing to tell players to use walls and ceilings rather than stacking foundations.

we start out with 2500 ceilings and ~540 Server-FPS

1. 2500 flagons (50x50 grid): ~297 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2448626999
   
2. 2500 flagons + 1 NPC (50x50 grid): ~175 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2448627624

summary: as each placeable is one actor by itself, adding 2500 decorative placeables is a huge performance hit.
adding NPCs to that area make performance even worse - most likely for pathfinding/collision reasons.

we start out with 2500 ceilings + 2500 flagons and ~297 Server-FPS

1. 2500 individual flagons + 25 collectors: ~284 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2448628142
   
2. 2500 individual flagons + 25 collectors + 16 NPCs: ~94 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2448628556
   
3. 2500 compressed flagons in 25 collectors: ~381 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2448629132
   
4. 2500 compressed flagons in 25 collectors + 16 NPCs: ~265 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2448629831

summary: while these tests are highly synthetic, it is clear that having a huge number of placeables on the server will bog down performance - even more so if there are many npcs around.
while a "no npcs around" boost from ~284 to ~381 is only 33% performance gain, seeing a "npcs around" boost from ~94 to ~265 is a impressive 181% performance gain.

we start out with 2500 foundations.

1. 2500 Sandstone Foundations (T1), ~335 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2567288836
   
2. 2500 Stonebrick Foundations (T2), ~335 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2567289279
   
3. 2500 Reinforced Stone Foundations (T3), ~335 Server-FPS
   https://steamcommunity.com/sharedfiles/filedetails/?id=2567289499

summary: while the polygon count increases with each tier level - the server performance does not change at all.

we start out with 2500 foundations, with 1 Standing Torch each.

1. 2500 Standing Torches, ~17-18 FPS client, ~425 FPS server.
   https://steamcommunity.com/sharedfiles/filedetails/?id=2567289892
   
2. 2500 Witchfire Torches, ~19-20 FPS client, ~425 FPS server.
   https://steamcommunity.com/sharedfiles/filedetails/?id=2567290117
   
3. 2500 Radium-Lights, ~17-18 FPS client, ~425 FPS server.
   https://steamcommunity.com/sharedfiles/filedetails/?id=2567290430
   
4. 2500 Glowing Goop-Lights, ~17-18 FPS client, ~425 FPS server.
   https://steamcommunity.com/sharedfiles/filedetails/?id=2567290719

summary: even with the additional "fire" and "smoke" particle effects, torches and radium light perform the same. anyone take a guess why the witchfire is less "expensive"?

we start out with 2500 foundations, with 1 Standing Torch each.

1. 2500 Standing Torches, ~17-18 FPS client, ~425 FPS server. Near instant replication.
   https://steamcommunity.com/sharedfiles/filedetails/?id=2567289892
   
2. 2500 Furnaces (empty), ~30 FPS client, ~165 FPS server. Quick but NOT instant replication.
   https://steamcommunity.com/sharedfiles/filedetails/?id=2579846045
   
3. 2500 Furnaces (active, coal, ironstones, no thrall), ~10 FPS client, ~165 FPS server. Slow replication with pauses every 8 seconds.
   https://steamcommunity.com/sharedfiles/filedetails/?id=2579846730
   
4. 2500 Furnaces (active, coal, ironstones, t1 thrall), ~2 FPS client, ~165 FPS server. Slow replication with pauses every 8 seconds.
   https://steamcommunity.com/sharedfiles/filedetails/?id=2579847106

summary: while there seems to be no performance difference server wise, having a filled storage affects replication speed a lot. also, having a lot of workbenches with thralls seems to bog down the client only.