SQL Read Committed Snapshot Isolation in Database with Selects and Inserts Only
Of course they can block each other. The values you're inserting for PersonName can end up anywhere in the index, unless your customers only place orders alphabetically.

Whenever you perform an insert, the value for PersonName gets inserted to the


Leaf of the clustered index
Key of ix_PersonName
Leaf of ix_CustomerGuid


These inserts will lock intermediate (for keys) and leaf pages (for includes/the clustered index), and may cause page splits on full pages.

Even though your Id and GUID columns are sequential, which should direct most of the INSERT work to the end of those indexes where you're theoretically less likely to be selecting data from, PersonName can be anywhere in the indexes.

That can lead to blocking for any query that needs to touch PersonName. 

Though singleton inserts should be brief, they can certainly pile up a bit, and may be hampered by any data synchronization (Mirroring, AGs), or just writing out to the transaction log (WRITELOG waits). 

In an INSERT/SELECT only workload, RCSI or SI would behave like the READPAST hint, where you'd skip past reading locked rows being inserted. 

Read Committed waits for write locks to commit or rollback, which can cause blocking in the same way that they could cause blocking waiting for an update or delete to finish.