Will higher shared_buffers improve tpcb-like benchmarks?

I'm going crazy trying to optimise my Postgres config for a production setting [1] Once I realised random changes weren't getting my anywhere, I finally purchased PostgreSQL 10 - Higher Performance [2] and understood the impact of shared_buffers.

IIUC, shared_buffers won't have any significant impact in the following scenario, right?

-- DB size = 30GB

-- shared_buffers = 2GB

-- workload = tpcb-like

This is because the tpcb-like workload selects & updates random rows from the DB [3]. Therefore, with a 2GB shared buffer, there is only a 6-7% chance (did I get my probability correct?) that the required data will be in the shared_buffer. Did I understand this correctly?

If nothing else becomes the bottleneck (eg. periodically writing dirty pages to disk), increasing the shared_buffers to 15GB+ should have a significant impact, for this DB-size and workload, right? (The system has 64 GB RAM)

[1] Related thread at https://www.postgresql.org/message-id/flat/CAPz%3D2oGdmvirLNX5kys%2BuiY7LKzCP4sTiXXob39qq6eDkEuk2Q%40mail.gmail.com

[2] https://www.packtpub.com/big-data-and-business-intelligence/postgresql-10-high-performance

[3] https://www.postgresql.org/docs/11/pgbench.html#id-1.9.4.10.7.2

-- Saurabh.