Fitting a bike properly is actually quite simple. Here's my fitting primer: How can I fitting my bike

Whatever position you are trying to use, just do those steps in order. BTW, more comfort is not necessarily more upright. Almost all long distance riders use the standard road bike position, back at about a 45° angle with elbows slightly bent. It is faster, but mostly because it's more comfortable when trying to produce power. One needs to have the torso out over the feet in order to be able to pedal strongly. Some of that is balance, some is the amount of hip bend.