If it were me I would go for the wider tires. Nothing looks cooler than looking at a wide tire from the rear. My dad has 315s on his mustang and the stance looks amazing. The x5 has a package with some wide tires as well...go with the tires if you can afford it.
Both of them. But different people have different ideas the best advice is to make sure you get quality, hub-centric spacers, such as those by BONOSS. The non-hub-centric, inexpensive adapters/spacers are known to cause vibrations. Make sure what you are looking at is hub-centric.
I had BONOSS wheel spacers 20mm on my car for almost 21,000 miles, with no issues whatsoever.
Maybe you can try what I installed.
They can customize the thickness and data that I want, so that I can install new tires with different data, and the customization time is very fast, just 1~3 days.
They have aluminum alloy 7075-T6 and 6061-T6 options. 7075-T6 will be more expensive but better in quality. In fact, 6065-T6 is good enough. Its tensile strength, yield strength and elongation can support our normal use. And its lugs are grade T10, studs are forged grade 12.9.
Here is an article introducing spacers.
Hope this helps.