Both areas are real "opinion" areas. Not any "right" ways, just lots of different "good ways". You have to decide what floats your boat, that YOU think looks easy to work with.

Many people just "T" the supply line to the carb inlet, and use that as fill/drain. WOrks fine.
Others like the three line deal - depends on you.

Throttle servo - less vibration back in the fuse, but harder to have slop-free, rigid throttle setup. Mounting the servo on the box has advantages too. short linkage, easier to maintain slop free, more accessible for setup/tweaking.

I put my servos on the engine boxes. I tee my fuel lines to the tank.