Hi!
Don't start with a 10x6 prop at least if you fly at sea-level...it is too small prop for all highwinged trainers using a .45-.46 engine.
The propeller you should use is a 11x6 APC ...both for running in and flying...no special running in prop is ever needed on modern engines.
As for a ball bearinged engines like the Magnum and TT compared to the OS LA plain bearing engines; I personally think the OS is the best engine for a newbie flying his/her higwinged trainer.
The reason for this is the OS LA:s lightweight and mild behavior. Light weight is of utmost importance in every airplane. Every gram counts! That you don't think of when you are a beginner.
Having a too powerful engine could also be hard to a beginner.....People often say" I can always throttle down" ...that is true...but what they don't think of is that power comes in different portions.....with the OS .40-.46 (or TT.42) it comes in a gentle and smooth way when you give full throttle....when you give full throttle to a ball bearinged engine the power response is more aggressive.......both engines will naturally respond instantly ....but with a ball bearinged engine the power increase will sometimes be too much.....at least for a beginner... making the airplane go all over the place and perhaps crashing just because the pilot did not have enough experience to cope with the shift in trim that occurred because of to much power when he gave full throttle.

I would strongly recommend a plain bearing engine like the TT .42 and OS LA .40 and .46 before a ballbearinged engine.
Your airplane will fly slower due to the lighter weight, The power increase when you give full power will come in a gent-lier way, less fuel is used, The engine will hold up for as many years as any ballbearing engine, No ballbearings that get rusty and could brake.
Perfect engine for a twin due to it's light weight and reliable behavior. Could stand a crash better due to smaller carb and no dirt in the ballbearings and cheaper to rebuild.
The only minus is it slightly lesser power output compared to a ball bearinged engine.


Regards!
Jan K
Sweden