Is there a way to set match so don’t have to pick heroes and soldiers every time?

In the hall of war building there is the option for Troop Form Set. This lets you set up a template for a march including the heroes and the troops up to your current maximum.

You will need to have reached VIP level 5 though to set up 1 and you can then unlock more sets as you increase your VIP level.

When you then join a rally or send out a march for any reason you can tap a small arrow at the bottom of the selection screen next to the Quick Select button to let you select from one of your saved 'Sets'.