Gears to go, Breake to slow.
This is how instructors have taught me to drive during my driving instructor training (cars) & would suggest it would be the same for bikes but being new to bikes, don't hold me to that.
There is a big difference between engine braking & braking braking with the gears (although basically they are the same, confused?)
Used to wash off speed as you approach 'whatever' and are anticipating the need to reduce speed to maintain flow. i.e. on approach to a 'meeting situation' or ped.x. etc. where reducing speed by a few mph will allow oncomming traffic to clear the 'meet' or the lights to go green. Selecting the correct gear for the reduced speed before accelerating.
Changing to a lower gear than current speed required to get increased engine braking to quickly slow the vehicle could 'lock' the rear wheels (or wheel on a bike) increasing the risk of a rear wheel skid. Similar effect to applying the handbrake/rear brake, a big no no & my riding instructor tell me front bakes at speed, rear brake when v-slow.
Brakes (bike front brake).
Designed to slow the vehicle & used correctly do the job perfectly (far better than gear braking), why use anything else?
Anticipation is the key to good driving/riding. For example.
A 'boy racer' races to the lights (on red) & slams the brakes on stopping 1/2 a car length over the line, into 1st & is ready to go on green.
I engine brake anticipating getting to the line on green at 25mph & selecting the correct gear ready to accelerate.
Who crosses the junction first? ME, I've got 25mph on the 'boy racer' & have been a lot kinder to the car.
So engine brake to wash off excess speed, brakes to slow to a stop or reduce speed more quickly than engine braking allows, gear braking NEVER.
My tuppence worth