As for your question about Roleplay;
There are a few different types of threads you can join. First there is the Open threads which can be started by you or anyone else. Basically this means these threads are open for anyone to join at anytime! For example there is
this thread here which is open, feel free to join it!
Then there are solo threads, basically these tend to be job threads or skill farming threads that players have a specific plan for. Therefore they do not want anyone else joining. You can make your own solo thread, but be sure not to join anyone elses without asking.
There are PM to join threads which are pretty self-explanatory. If you want to join the thread make sure you ask the creator. Again you can create this type of thread yourself.
Then there are
flashback threads. These are threads that are conducted in the past during a season that your PC was not created. This means you can create a flashback in any season before Fall of 516 since your PC was created during this season.
All of these threads usually have markers to indicate what kind of thread they are.
Other than that there are threads in which you gather a group of PCs beforehand and construct a basic plotline. This is the most common type of group thread. Just look at the registry and PM someone who looks interesting! (Though I will warn you the only active PCs right now are Sira, Azira and Kovac.)
There are a few more types of threads such as quests and their description can be found
here.Here are some good terms to know about Play-by-Post RP and Mizahar.