Does Partition Creation Order Matter?
...if the order of the partition id is not in sequence with the partition key order


SQL Server always maintains partition ids in partition boundary order. No matter how you split or merge partitions, the order of boundary values always matches the order of partition ids. SQL Server renumbers as necessary.

Concerning performance of the split operation itself, you will want to organize things so that the minimum (ideally, none at all) physical data movement occurs. This typically involves careful thought and testing in advance, using SWITCH and CREATE INDEX…WITH DROP_EXISTING = ON.

Review the following all by Dan Guzman:


Table Partitioning Best Practices
Remediating a Table Partitioning Mess
Move a Partition to a Different File Group Efficiently


If you need help designing the process, ask a new question with DDL for the table, indexes, partitioning scheme, function, and file groups. Also include a clear representation of the start and end states i.e. which data should go where.