Multi-tasking is overall slower than multi-programming, due to the overhead of context switching

Linux has different time slices for different processes.
The length of the time slice is decided by the niceness, which ranges from $-20$ to $19$

Priority number usually ranges from $0$ to $139$
$0-99$ are 'real time' priority
$100-139$ are non-real time/conventional priority

$-ve$ nice values need root access to be set

$120$ is the default nice value for user processes