How can I configure Ola Hallengren IndexOptimize script to run against a subset of tables
Don't defrag your indexes every night. You don't need to anymore on modern hardware (especially with solid-state storage with zero seek times). For daily maintenance, you only need to update modified statistics, and even then you only need to do this when you notice performance degradation (i.e. check what your monitoring system tells you).

Per Ola's site, you can do something like this:

EXECUTE dbo.IndexOptimize
@Databases = 'USER_DATABASES',
@FragmentationLow = NULL,
@FragmentationMedium = NULL,
@FragmentationHigh = NULL,
@UpdateStatistics = 'ALL',
@OnlyModifiedStatistics = 'Y'


The other thing you can do, for when you do need to defragment indexes (if for example you have deleted a large amount of data), is using SQL Server's Service Broker to set up the maintenance plan for multiple tables in a batch.

That article is in-depth and difficult to summarise in this reply, but it comes down to creating an asynchronous queue, that fires Agent jobs in parallel.