Best Practice for Invoice Numbers of Service Clients (on top of Ecommerce Product Orders)

I sell accessories for wedding photography on my website, and also photograph weddings as a professional service.

1. If I get 91 orders for Shopify products (Invoice 1001-1091) and then book a wedding client (not through Shopify, just word of mouth.) should I make their invoice 1092? Or is it ok to have my clients maintain their own independent numbering system?
2. Would I be better of processing the clients through my shopify to keep all records in one place? This helps determine when I am no longer a small supplier @ 30K over 4 quarters. I am just skeptical of the shopify fees as some of my clients e transfer. (no fee)
3. If I manually indepedently invoice my client for #1092, how can I skip that number for the incoming orders – so to speak.

Thank you for your help!