fat burn qns

[acema]

hi guys, have some qns.
as my bf is ard 17%, so i dun mind burning muscle mass too.

i would like to ask if.

20min of run targeted at 80% of ur maximum heart rate burns more fats.

or 40 min of incline walk/jog targeted at 60% of your maximum heart rate burn more fats?

[acema]

and to mention that i do cardio after lifting.
just want to know which is more effective as i wanna lose weight fast n cut down(dun mind losing muscle mass)

and i oso heard it tk 30min of cardio/excerise for your body to start to burn fats.
and as i will be doin the cardio rite after my lifting.