How do you mean? Front wheels stand vertical and the axle is just an m20 or smaller. It depends on what you want yo use.
You can ad a quick release if you want.
I used the warrior design for my first build.
I made parts my own way, but used the design as a guide line and gel with surten things.
That is not a problem. The design is vertical, but you can put them in an angle. I will probably do that also a bit. It widens the wheel base in the front, without making the trike wider. Gives you a bit more stability in corners.
A little lean in at the top can help cornering stability as Emiel says. It can also help the tyre stay on the rim instead of trying to roll it off in a corner. It will put slightly more strain on the wheel bearings but isn't likely to be any issue that normal servicing can't sort.
Best way is making an u shape opening instead of a hole. Just like the rear. But because it is mounted on one side, know that it can become weaker. So a bit thicker mounting would help.
I've yet to see any system that could undo a disc braked trike wheel without taking the calliper off so yes. What type of Q/R does it have? I'm hoping it isn't a std Q/R skewer through a 3/8 axle.