which gear to select at wat speeds depends on ur gear ratio and rpm when u drop to a particular gear. engine braking is only effective from the region above 3k rpms so, u will have to adjust the gear u choose to drop to, to provide u with optimal engine braking effect. for normal driving, engine braking from 4k rpms downwards is acceptable. but if racing, i may use engine braking up to 8k rpms.

but using engine brakes at high rpms results in more stress not only to the gear box, but also to the engine as well so try to restrict its usage to low rpms for normal driving. at 80 km/h drop to 2nd gear abit hi if u ask me. the abrupt weight transfer to the front will cause the rear to lose traction and result in a spin out if u are going thru a corner.
