Can iphone 7 plus charge to 87 watts adapter?

Yes, with a USB-C to Lightning cable. It won't charge significantly faster however.

See below from USB-C to Lightning Cable (1 m) - Apple

Connect your iPhone, iPad, or iPod with Lightning connector to your usb-c or Thunderbolt 3 (usb-c) enabled Mac for syncing and charging.

You can also use this cable with your Apple 29W, 61W, or 87W usb-c Power Adapter to charge your iOS device, and even take advantage of the fast-charging feature on iPad Pro, iPhone 8, iPhone 8 Plus, and iPhone X.

Yes, but when I measure the power it pulls, it's only 1.2A at 4.9v (5.9 watts). So it's marginally faster than the charger it comes with, but far less than the maximum an iPad charger can deliver (10 or 12 watts depending on model).

The fastest charging comes from plugging in my iPhone directly into my laptop MacBook Pro Retina. I suspect that's because the iPhone negotiates an "Extra Operating Current" of 1.6A (in addition to the 0.5A that USB provides) for a total of 2.1A. This can be seen by going to "About this Mac" at the top left, then "System Report", then "USB", then selecting "iPhone". When connected to chargers, the iPhone instead reads the resistance of the data pins relative to VCC.