depends on what you concider as a crash. In general, as long as you're able to reconnect your content, configuration and Nintex databases you will be able to reset your farm to the time the backup was done. It's kind of the same process as migrating Nintex Workflow from one server edition to another.
Hi Enrico Knapp,
Yes it really depends on the crash.
As per my understanding, even if the w3wp.exe process restart. Workflows run in different process (owstimer.exe) so your workflows continuing run without any problem and if for some reason the task owstimer.exe process ends, workflows stop to run and will be run again in the next time as is setting.
Correct me if I am wrong :-).