[quote="Zotged":20r9lmez]if I use external textures as in load files to fill sprites are the external textures all converted to PNG before the app runs?[/quote:20r9lmez]
If you mean actions like "Load frame from file" at runtime, then no, they're decompressed and loaded directly in to video memory. There would be no point converting the file to PNG then loading in to video memory! That would be the same as decompress source file -> recompress source file as PNG -> decompress PNG -> load to video memory!
[quote:20r9lmez]Is it faster to use external textures instead of ones inside the cap?[/quote:20r9lmez]
Probably not, it would only affect the startup time, and if the startup time of your application is fine, there's no point caring.
[quote:20r9lmez]When I add a sprite to Construct it converts it to a PNG, but if it's loaded in the runtime will Construct convert it to a PNG as well?[/quote:20r9lmez]
As I said earlier, once images are saved in Construct, they stay PNG, and the runtime loads them as PNG.
Basically, to summarise the system:
Images in Construct are stored as PNG, given to the runtime, and then decompressed to video memory on startup or another time (depending on your texture loading settings).
Images loaded at runtime are immediately decompressed to video memory.