Personally, I'd wait for a couple more releases on the Surface Book before purchasing. You can buy other touchscreen laptops/mobile workstations that would fit your requirements.
My question to you is how much rendering and simulation are you talking about? I would not recommend any of the Surface products if you will be relying on these devices for those activities.
The Surface line is meant to replace a "laptop" not a workstation!
Now, after saying this you can do rendering and some simulation. Just don't expect too much in those regards.
Personally, I'd go for a Surface Pro 4. It is a more mature product line, you can get similar hardware configurations and it can also hook up to multiple monitors (if your monitors support DisplayPort 1.2) with a single cable out or you can use the portable docking block.
I recently saw an article comparing the surface pro 4 to the surface book for gaming and the discrete GPU on the SB was significantly better than the integrated graphics on the SP4. Now, a lot of what Solid Edge does is single thread CPU related and for that the general advice is to get the highest clock speed as possible, but graphics performance is also hugely important so of the two machines I'd go for the i7+GPU or i5+GPU surfce book depending on your budget.
I'm thinking this if you need a tablet with a pen: http://shop.lenovo.com/us/en/laptops/thinkpad/p-series/p40-yoga/
Not a detachable but a convertable. Uses a Wacom pen with 2048 levels of pressure sensitivity (important for those artist types) and it stores in the body of the PC, not hanging on the outside using a magnet... Also sporting the latest QUADRO GPU!
Found this for my daughter who thought she wanted the Surface Book, but a potentially better option for her as a graphic designer/artist.
Hold on...I don't think it wise to compare DirectX games running on a device and saying you will get better performance from your OpenGL api calls on your CAD programs. Yes, there are plenty of debates you can find about OpenGL vrs. DirectX and the CAD programs.
Maybe someone from Siemens PLM Solid Edge group can pipe in as to what type of apis are being used by Solid Edge these days? OpenGL or DirectX.
Anyway, if you want a decent comparable I found this website that compares the Surface product lines. This doesn't include anything about the Surface Book. What I did find was there is a lot of passion between the two groups- SP and SB. Each saying their device is better.
If we reflect back on your requirements: 1) Run CAD, 2) Run Simulation, 3) Run Rendering, 4) Mobility
I would still advice you on purchasing a laptop. Something like the Boxx SLM. With this laptop you would still be able to replace components if something failed in the hardware. You just won't be able to do that with a SB or SP.
I am currently using the Microsoft Surface book as my main computer to run Solid Edge ST8. Due to the work I do, I needed a portable platform to work from. When working with it as a workstation in my office I have a docking station plugged in and run a 27" Monitor.
The model I have is an i7 processor with the dedicated GPU.
Solid Edge nearly works with it. For some parts the graphics is OK but it is by no means perfect. PMI dimension (Just the numbers) disappear sometimes. Open a part form within an assembly and the graphics really slows down, movement is so slow. At odd times the surfaces disappear and either become invisible or turn into lines with triangles all over them.
The issues above are frequent and very random. Possibly due to the lack of memory. The image below shows the stats for the laptop.
Here is a classic example of the moody graphics. The first image is showing a highlighted face on a part. It shows how sometimes the graphics cannot handle the surfaces very well. The one after is after restarting Solid Edge and opening the assembly again and shows the face in the normal way.
As you can see, quite a difference. And at times the PMI dimensions values will disappear as mentioned above. All there is are the projection lines, the arrows and dots where the numbers should be. Clicking on the central dot will bring up the dialog box to change the value. It is a pain however. I managed to get it to repeat the dimension issue. See image below.
On a more positive side, updates are coming out thick and fast and some issues I had originally with the monitor have been fixed. But many issues still remain.
I hope that helps. If you can, you should wait.