Are there any SQL Maint Plans that need to be created for 4.5/4.6?

Yes, it is recommended. Regular database maintenance as per Microsoft best practise is required on all K2 databases.

If the fragmentation of CLUSTERED/NONCLUSTERED INDEX is over 40%, rebuild the index, if it is less than 40%, reorganise the index. As always, make sure you have a valid backup before doing any database maintenance. Stop K2service before rebuild/reorganize the indexes.

The size of tempdb can also affect the performance of a system. For example, if the tempdb size is small, the system processing could be too occupied with autogrowing the database to support your workload requirement. You can avoid this overhead by increasing the size of tempdb.