You can probably have 100s of thousands of Instances on most devices without any problems, unless you run out of RAM this shouldn’t be an issue by itself.
As for number of parts, that highly depends on the complexity of the parts,i.e the total amounts of triangles used to draw those parts and wether or not they are Anchored, these two things are just as important than the actual amount.
Use Shift + F2 to see the total amount of triangles drawn in any given frame, from what I have seen on the frontpage ~500.000 maximum triangles drawn is a good number to aim for and will perform well for most potatoes/mobile devices.
My PC is fairly old (8 years) and doesn’t have anything decent…Games start lagging for me at about 30K-50K parts, depending on size, if if any are unions.
Most people have nice enough PCs that can handle 100K+
But for mine, like I said…it’s old. Unions are a huge issue for me, they lag like crazy if I have more than 50.
There isn’t really a “Set Amount” But you just have to consider who might be playing the game, and if you want it to still run well on older PCs.
Hope this helps.
This might not have even made any sense. Hope it did though…
My voxel procedural terrain generates up to 400K parts(Only cube parts with 12 triangles) until the server crashed. Whoops. While my mid-tier PC survived with minimal fps drops. I think beefier PCs can handle more, but Roblox’s servers themselves are limited in RAM.
Afterwards I had to add a cap for the number of voxel it generates.
Converting complex unions to meshes, that reduces lag. There have been a rumor in ROBLOX for so long that unions reduce lag, which I don’t agree to. You can also try sorting stuff in folders, that will balance the game as well.