It is possible to only show autobids for auctions rather than allowing incremental bidding by editing your Auctioneer settings. Click here to see how to access your auctioneer settings.
Once you are editing your auctioneer, go to the Main Settings tab and scroll down to the Bidding section. Here you will find a tickbox labelled Show Autobids Only. Tick this to hide the bid button and display only the autobid option for lots:
Once you have made any changes as required, click the green Save Auctioneer button at the top of the screen.