Thanks for coming back to our forum and updating us about your concern, @HPTT.

I can share some more insights with you about this topic. Yes, at the moment price rules is not yet available in Singapore versions of QuickBooks. If you need to use different prices for customers, you'll need to manually edit the price on the invoices for now.

The performance of your QuickBooks account is not affected by the number of lists you add to your products and services. You can check this link to learn what causes QBO to perform poorly:  Why is my QuickBooks Online slow?

Please come back here if you need further insights about the program features. I'll be right here to help you out.