Hi Aidan,
Create your publication in 1024 x 768 as you typically want.
To have the pub resize automatically to fit any screen resolution go to the "Chapter Properties" and tick the "Resizing" option. Also tick the Horizontally, Vertically and Maintain aspect ratio options.
You can leave the four max and min parameters on the right all unticked. Or, if you want to set limitations you can custom set your preferences. The Opus HELP file elaborates on these features.
Aidan wrote:
<< Firstly, when I create my new publication, which option should I choose (Scale publication, temporarily fit or keep original size)? >>
You must be creating new pubs using the Wizard Mode. In your case "Scale Publication". You can edit the Chapter Properties as mentioned above afterwards.
Aidan wrote:
<< Then what settings should I apply in Page and chapter properties please?
You would select 1024 x 768 since you wanted this as your default. Your pub viewed on any other size will either shrink-to-fit, or stretch-to-expand (Resize).
Hope this helps.