Can I Show Only Certain Line Items to the client?

Yes! You have 3 options to control what the client see's on the quote:

1. Billable/non-billable line items - By toggling the billable check box on the quote, you can choose whether the client will see the individual line item. You’ll always be able to see it in the background, but this gives you control over quoting with every line item visible, or just quoting the client a fixed price or prices by adding line items just to display the billable pricing.
2. Phases - Quote phases let you group task and product line items together, so you can display just the phase totals, not the individual line items to the client.
3. Document templates - You can customise your quote document templates to display or hide certain elements on the quote itself.  For example you can just display the quote or option totals and not include the line items at all.