Does having High Baud rate Guarantee High spectral efficiency/OSNR?

In this article let us have an overview of spectral efficiency (measured in B/S/HZ) if case we have high baud rates (which is the symbol rate measured typically in Gbaud)

Let us understand this via an example , let us say we have two baud rates of 30Gbaud (arbitrary number for example) and 40Gbaud respectively and we want to use DP QPSK modulation which means 4bits/symbol .

So in this case the capacity we can fetch will be Capacity theoretically ~ 120G and 160G considering 20% FEC lets say we can transmit 100G in both cases . Now let us say we have 50Ghz channel spacing then we have spectral efficiency in both cases it will be 100/50 which will be 2bits/sec/HZ .

So we can see that only merely increasing the baud rate does not increase spectral efficiency .But if we change the modulation to let us say 8QAM the spectral efficiency increases isnt it ?

But then there is a well known trade off between complex modulations and reach. So what is the solution to all of these ?l high baud rates? Higher bandwidth with improved OSNR- The answer to all of them is PCS (probabilistic constellation shaping).If we use PCS modulation we can achieve high bandwidth and better OSNR