1. 240Hz, Asus ROG Swift PG258Q, TN monitor w/ G-Sync support.
(Just an example)
2. Yes, ofcourse. It won't look smoother than your monitor's highest refresh rate though. It can only make your monitor more responsive to user input, when playing at a signficantly higher framerate compared to your refresh rate.
Monitor: Asus ROG Swift PG258Q 24.5" 1920x1080 240Hz Monitor ($599.00 @ Amazon)
Total: $599.00
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-04-05 03:35 EDT-0400
More 240Hz monitors are listed here:
http://www.144hzmonitors.com/gaming-monitor-list-120hz-144hz-165hz-200hz-240hz/