executor docs

[hros]

I recently saw Alan Edelman's video on parallel processing using FLoops. He used the ThreadedEx keyword to specify the number of cores used The docs mention the three Executors (Threaded, Sequential, Distributed) but do not provide any explanations on the arguments and usage

1. what is the default action of ThreadedEx()? is it to use all available cores?
2. are there other arguments other than the number of cores to use?
3. Is it possible to perform "composable parallelism", i.e. FLoop an inner loop while controlling the available number of cores to each loop? btw, what about the usage of the other two executors?