As stated often on this and other forums, frame material is only part of the equation, the design of the frame and quality of the build has far more impact on the comfort.

Any genuine track frame (as opposed to those that pretend to be) will be poor on comfort because it's not a design requirement for a bike intended for a smooth velodrome with performance the ultimate aim.
There are frames designed for the street and these will be more comfortable.
Aero is important but the more aero your position, the less comfortable it will be over any distance (you need to be very fit, strong and flexible to maintain a racing position).

Better frames use better tubing, have more time spent on the design and are built with more care, consequently, they cost more.

And we haven't even got into components yet, while the most important thing is how it's set up.

You've got a bike now so can make a good guess on how this bike will be used - this determines the type of bike.
Decide how much you can spend and over what period - you can build a bike in one hit or build it up as you can afford it. Remember, the frame is just a component and can be replaced at any time.
Then consider yourself and how much work you're willing to put into your own strength and fitness - my bikes will always be more conservative than my hyper-fit son's.

We can't answer these questions for you. Specific questions yes.

For what it's worth, I'd buy a quality steel frame, drop bars for most hand positions and best aero, dressed with good quality components.