You can use any wood you like. The bench I am using right now is a Nicholson bench made out of douglas fir. There at least 2 schools of thought on wood type for a bench.
The first one us use a hardwood for the top. Because it will last longer.
The other is use a soft wood for the top. Because if you bump the piece you are working on, the bench will take the hit and not your project piece.
Truthfully I don’t think it really matters. Use what you can afford, and what is plentiful in your area. What does matter is the weight of the bench. You don’t want it to move when you are planing on it. By me the affordable hardwood is white ash. They are cutting down a lot of ash trees, because of the emerald ash borer. If you look at historic benches. They used what was plentiful and local.
You don’t need a one piece slab. You can make a top by laminating several boards together. A thick slab big enough for a workbench can be expensive, and harder to find. Personally I like the look of a laminated top. It is a preference thing. Its your bench, it should look like what you want it to look like.
You will need to make the vise, but you don’t need to use a wooden screw. Last time I looked a wooden screw was about $200. A metal one from Lee Valley was about $45. Both screws work just fine.
The age old question, do you need a bench to build a bench. Not really. If you start with the top first, you can clamp it to a couple of saw horses and work off of that.
The video on making a Moravian workbench is very well made, and is easy to follow. Will is very good at explaining what he is doing, and showing the joinery. The camera work is also very well done. It is one of the best videos on how to make a workbench.