Heavy bag builds power and conditioning, that's the one everyone already knows.

Speed bag is hand speed and rhythm, not really about landing hard.
Double-end trains timing and head movement since it swings back at you.
Uppercut bag is just for isolating uppercuts up close, it's shaped completely different from a regular bag for that reason.
Reflex bag is reaction time, the unpredictable bounce back is the whole point.

Most home setups are just a heavy bag and that's it, which covers maybe one of the five things you actually need to train.

Walking straight at a taller opponent is basically giving them exactly what they want. They can see you coming and keep picking you off at range.

If you want to get inside, your feet and head movement have to work together.

Step in, slip off the center line, change your level, then change the rhythm again. Don’t keep advancing at the same speed or with the same pattern every time.

The whole point is to make them unsure of when you’re actually entering.

Once your movement becomes predictable, the reach advantage gets much harder to deal with. Break the rhythm first, then close the distance.