Fitbit and MFP

Hi. Just getting back into this and have purchased a Fitbit Charge 3 and have a treadmill coming. I get a bit confused with calories left and variances between two apps etc so trying to keep it simple.

Just want to make sure I am on track if I:

FOOD/CALORIES

Just use MFP to log food and stay within my 1600 calories and sync that to Fitbit.
Then i am just basing where I am off Fitbit - keeping track of calories burned plus extra from exercise - and I make sure each day I am at least 500 calories burned more than I eat from MFP.

I am eating around 1600-1700 a day and seem to be burning 2500 to 3000 a day depending on exercise. My logging is not quite 100% but getting there so I am not eating exercise calories back and will see how this goes.

EXERCISE

I only switch on recording exercise if I go for a walk or use treadmill.
If I MTB i will just let fitbit adjust calories off heartrate OR should I log the exercise????

Aiming to do 10,000 steps but with a sitting down job some days under and exercise day go over.