Your AS SSD write speed results are typical for a SandForce controller based SSD. They don't perform as well in write performance with non-compressible data, which is what AS SSD uses for its testing. Intel does show in their detailed specs the difference in performance with compressible and non-compressible data, and your results are not far from those specs.
Boot time is not from the time the power button is pressed until the Windows desktop is displayed. That includes the POST (Power On Self Test) time of the board, and the time it takes for HDDs to start up (usually spec'd at ~10 seconds), for all the onboard controllers to start, and whatever unseen activity the UEFI/BIOS is performing. That varies quite a bit between manufactures, and also depends on the amount of hardware you have connected to the board. Having the CPU over clocked speeds up the process, and having CPU power saving options enabled will slow it down.
Boot time starts when the Windows "Starting Windows" screen is displayed. If you have a password set, that also takes time to perform, as well as be displayed by the PC.
People with the super fast start up times have their PCs configured just for that purpose, plus they have a mother board that has a quick POST. They will have one drive on the PC, most likely a SSD. They will disable any devices they can in the BIOS, from extra SATA chipsets, to audio capability, and USB ports. The PC is likely over clocked, with some of the usual WIndows Services (there are all kinds of them) disabled.
A fast starting PC is part luck, with a fast starting mother board, and part configuration, and just seeing the time it takes for a PC to start does not tell us anything about what has been done to the PC to accomplish that. My ASUS boards take twice as long to start than my ASRock board does, each with very similar features and chipsets. In the old days, you could set the BIOS to check the memory, which would take a long time, and the POST process would tell you what it was doing along the way. If your board has a POST code display, check the list of things that happen during POST, there are dozens of them. A "slow" starting PC is not a sign of bad performance or problems necessarily, but a good part of it can be manipulated by the owner.