Long and steady burns fat. Fat burning does drop off as intensity goes up, but not by enough to really worry about (and negated by the continued burning of fat whilst muscles repair afterwards).
Simply put you need to do as much as possible, which means not straining yourself and missing the next ride as a result. Better to do a 1 hour ride you can repeat every day, than a 1 hour ride you need days recovery from. Even better, a 3 hour ride you can repeat every day.
So as many miles as possible, with as few hills as possible. Within reason, you need to want to go out riding, so keep it interesting! No harm in swapping a ride for a 40min spin class or goin out chasing stava leaderboards on the local hill if you really don’t feel like a long ride, or vice versa, go for a pootle round the country lanes if you don’t feel like tacking that killer loop you had planned. Staying motivated to ride every day is as hard as the actual physiological effects of riding.
I find riding to work, then riding to the shops a mile away rather than get my lunch downstairs motivates me more to go out riding in the evenings than not riding, so it becomes a self fulfilling thing.