I am also preparing for a KoS attempt and based on the training plan I expect to give it a go on 12/12. To your questions, @Coach.Neal.H has a post higher up in this feed stating that Epic Days Do Not Require Epic Training - Knighthood that includes some suggestions on how to tackle the day itself. Although the Epic Day may require some Epic Recovery.
I would think if you are in overall good fitness, making the adjustments you are considering should not negatively impact your effort. It is just nice enough here in Chicago that I will be riding outside at least one day this weekend and will make sure it is of similar duration as the plan lays out.
My preference is to get it done before the holidays. I will be physically fit enough. More concerned that if I push it of one week, it will be easy to push it off two or more weeks.
I have done three videos back-to-back and agree - it is much more mental than physical. Although my legs buzzed all day.
I had trained all last fall and winter for a spring gran fondo that was cancelled. In retrospect I should have done the KoS challenge that day. Oh well, no time like the present.