Size 11 is also what I am and is a hard size to buy snowboards for. The cutoff point for when you should get a wide board is usually size 11 for most companies. This means that normal boards are usually a little bit too narrow for us, and wide boards are usually a little bit too wide for us. Snowboard widths are normally given at the widest part of the nose, the narrowest part in the middle (the waist), and the widest part at the tail. The problem with having these measurements is that your feet go inbetween these points. The board I am riding right now is not a wide board and I havent had too many problems with it. Every once in a while if I'm doing a really hard carve, where I'm really leaning into it, my toes will drag and cause me to fall. But I really have to get the board up on an angle for this to happen, much more of an angle than a beginner/intermediate rider would do. It hasnt been enough of an issue for me to care too much and if it did end up bothering me too much, I could always just buy some risers to put under my bindings.

I would say that a normal to medium width board would probably be fine for you right now. But the best thing for you to do would be to go to a shop and ask someone there. Look at some size 11 boots and put them on top of a board in the angle that you would want them in. A small amount of overhang is ok but you dont want too much. Worst case scenario if you get a board and find that your toes are dragging, you can angle your stance a few more degrees and/or buy some risers. Another thing to remember is that different brands/styles of boots will be different lengths even though they are the same size on the inside.

As to the length of the board, for someone of your weight and ability, I would probably recommend something around 158 plus or minus a few centimeters. This is short enough that it should be pretty easy for you to control and long enough that as your skills progress, it wont be holding you back. There are a lot of online calculators out there where you can punch in your weight, hieght, riding style, etc. that recommend what length of board you should get but you could put the exact same info into all of them and still get different answers. There is no set rule, its all just a matter of opinion. I think people put too much emphasis on the lengths of boards. Look at a ruler, see how long 3 cm is? Barely over an inch. On a board that is almost as tall as you are, an inch isn't really going to make that much of a difference in my opinion. The lengths of boards are usually given from the very tip of the nose to the very tip of the tail in a straight line. Some boards might have a big nose and tail that curve way up while other boards might have small nose and tail that aren't very long. This means that 2 boards which say they are the same length have very different effective edge lengths. If you find a board you really like that isn't exactly the right length you are looking for, I say dont worry about it too much, just get it and have fun.