Others may have a better advice on which brand/type to buy, but here are a few definitions of your questions.

1) Direct drive - A Direct Drive Starter has the bendix (Starter Drive Gear) mounted on the starter motor's shaft. It spins the same speed as the starter. It usually spins the engines faster but a larger/high compression engine requires a larger electric motor.

3) Gear reduction - A Gear reduction starter has the Bendix mounted to a separate shaft from the electric motor/Armature shaft. A gear(s) connects the two shafts and reduces the number of times the bendix turns in relation to the motor shaft. This acts like first gear in a transmission. More torque to turn the engine so a smaller electrical motor can be used but it will typically spin the motor a little slower.

4) Mini Starter - A more compact design starter. Almost always a gear reduction type starter since the electric motor is the largest part of the starter assembly and a gear reduction system allows a smaller faster spinning electric motor to be used in place of a larger torque motor.

2 Permanent Magnet - Electric motors operate by using magnetic fields to push/pull the armature to cause it to spin. Think about trying to put two magnets together and how they attract or repulse depending on the way they are positioned. Most high power AC/DC motors use the electric current flowing through coils mounted around the armature (Motor Housing) and coils inside the armature (Motor Shaft) to create an electric fields to drive (Turn) the motor. Permanent magnet motors use coils in the housing or armature and Permanant magnets in the other to create the magnetic fields to drive the motor.

All starters are either direct or gear reduction by design.

Either of those designs can be a Mini design, permanent magnet design or both.

I hope it helps.