does the use of bsa files increase the file size?

bsa files use compression which makes the file size smaller

do bsa increase or decrease performance?

it increases performance because the files are read directly from the bsa without having to be decompressed, and because the files are compressed it allows the files to be read and loaded faster

do bsa files take up extra system resources?

no, it actually uses less resources because the files have been compressed which means that they need less ram & vram in order to be used. so in reality they actually use less system resources

does it take long to make bsa files?

it can take a while if you have a lot of files to compress or if your hardware is not very good. but with good hardware it usually takes a few seconds to a few minutes.

why do some mod authors not use bsa files?

some mods will not work correctly if the files are put into a bsa, but the main problem usually comes from the mod authors not knowing how bsa files work or in some cases the mod author cannot or simply does not want to do the extra work

does this increase the size of zip, rar or 7zp files?

no it will make the files smaller because the files in the bsa are smaller