For data engineering exam Free Edition will be good enough. You can learn most things required by exam objectives there. Regarding Spark UI - if you have an access to labs then you can use classic compute as @BS_THE_ANALYST . If you don't have access and you don't want to spend money for that - you OSS Spark (the easiest way is to use docker container).

But don't focus too much on analyzing Spark UI plans - on exam you can get 1-2 question regarding this.

And as always - the best resource to prepare is to use Data Enginnering Learning path on Databricks Academy