I prefer flat and very lightly angled with low profile keycaps. That's not really done for a mechanical keyboard, and out of common modern keyboards (maybe Cherry), I've come to appreciate Filco profile (+Cherry-height keycaps) and case style the most (with feet not extended). I can type comfortably on that without a wrist rest. For anything taller than that, I need wrist rests. Those, I think, should either be soft or if not, they are a lot more comfortable with a slant rather than being solid rectangular.
This is a function of how low or high your desk is with respect to your chest. If your chair is too low or desk is too high, it's going to be uncomfortable to type on tall keyboards, and the angle at which your arms are positioned will be different than if you sit comfortably tall over the desk surface. Based on that, your need for a wristrest will vary, and you may find that you want a bit of an incline to your keyboard or no incline. (This is why I'm getting a taller chair for my home desk, as it's too tall, and typing + using the mouse for long periods of time is uncomfortable).