Bottleneck is the wrong term. Faster RAM especially with Ryzen cpu's can bring better performance. Not having enough RAM can cause issues like stuttering or excessive cpu and hdd/ssd usage. Most systems support dual channel RAM, the best gaming combination for dual channel is 2x8gb. 2x4gb is the bare minimum and will stutter in some games, 2x16gb is over the top with no benefit over 2x8gb.
RAM can have a big impact on a PC when it comes to gaming or doing pretty much anything. A lot of new games are using well over 8GB of RAM if you want to run them on high settings. To answer your second question "can 8gb RAM bottleneck a 2080" the answer would be yes...or kind of yes. If you plan on getting a 2080 I would recommend 16GB at least and 3000MHZ is fine for most uses