I would take it easy on the bike with your marathon coming up, and then plug your next race into Plan Builder.
The TR plans (any volume) will build you up for any IM race. There is no truly different training required for different courses, but as you near race day finding similar terrain and conditions is useful. The reason it doesn’t make much difference is that you are aiming for a consistent a power output as you can over several hours of aerobic output.
Come and introduce yourself over here, lots of people training for Ironman races 