RE: engine side and down thrust
A plane all set up to zero angles will fly well. It will not fly at it's best, but it will fly well enough to get going until all small quirks are trimmed out. The need to trim out the plane depends on whether you have automatic thumbs that even out the plane's deviations, or whether you need it to be neutral through all manoevres. BTW, That is the holy grail of all plane designers. Some come close.