You are correct. It is simple in Tableau to configure SSO as it helps you generate the necessary keytab files. You can take a look at this link http://onlinehelp.tableau.com/current/server/en-us/qs_kerberos.html
- It does not matter if you use 128 or 256, It should work for both
- Session timeout depends on not only your Active directory user, but also Tableau can its own session for users which you can modify using tabcmd
- You may want to configure domain delegation if you want to use Tableau to do SSO with SQL Server, etc.
In addition to Shankar's points, here is an introductory video that walks through the full end to end configuration. Though the video is based on 8.3 version of product, it's still applicable in 9.0.x. We have tried to make kerberos configuration a lot more simpler by providing automatic script generation which gives you a script that your AD admins can execute to set up the SPNs etc.
This video does not talk about the delegation settings. Also would like to see some documentation around how to setup kerberos SSO for MSSQL services in a load balanced environment. The config tool that Tableau provides does not seem to be considering these options i.e. Load balanced aware configuration. Unless I have to make any changes in my config file.