MacBook – Sufficient ssd for Mac

SD cards are categorized in different classes according to their speed. Generally, SD cards perform even slower than a normal HDD drive which is why I do not recommend using them as a major storage option.

You should invest in the most expensive type of SD to have an acceptable I/O performance. E.g. an Ultra High Speed SD card (UHS) such as this one.

For $179 you get 128GB storage which is even more expensive than some SSDs models at that capacity. But the I/O throughput is much lower. The minimum guarantee is only 60MB/s for this particular model. SSDs in the same prize category offer up to 550MB/s of transfer speeds.

In sum, you're better off using an external SSD an connect it via USB 3.0 or Thunderbolt for best I/O throughput.

You can't run Bootcamp from an external hard drive, but you can install Windows via a virtual machine (MV Ware or Parallels are the best known). If you install Windows on the internal drive you have the option of booting from it directly or using one of the VM machines while running Mac OS.

As for the hard drive size you should consider the 768GB drive if possible. The drive space goes quickly and isn't upgradable. (Well, it is, but AFAIK nobody makes larger or faster replacement drives.)

The OSs run independently of each other, so you don't have to worry about cross-contamination. When running BootCamp you can't even see the Macintosh partition.

In my experience it works as well as can be expected considering the limitations of running software on hardware that wasn't specifically designed for it.

Good Luck.