I use tq wrench on drain but never on Derby or inspection cover. What's the worse that happens they weep and you can see it. Never has for me.

My 4 wheelers, sleds, tractor I don't. But it's easy to find in Harley manual. Though I am sure it is in other manuals too.

Either way the guy should own tq wrench

 

T27 torx

 

14-21 Foot Pounds for drain plugs, a 3/8 drive torque wrench will be fine.

I`ve been a professional aircraft mechanic for 50 years now, and I always use a torque wrench for drain plugs.

 

The reason people think torq are bad is because they use t25s

 

Well ... I never changed the oil on an airplane ... But as ASE certified ( Originally NIASE ) since 1972 I think I've got it covered ":>)

 

As someone posted T27 on Derby cover also follow the star pattern when tightening the screws. I've seen too many just go in a circle!

 

See post 7.
No, not needed, but lifelong torque (high quality) wrenches are an asset.
3/8 and 1/4 if on a budget and forego the 1/2.
FWIW, I would not buy the Harbor Freight set.