my sport is cycling, and I am pretty new. It is my understanding that training load is marked relative to FTP if you have a power meter, and Fitness is also measured relative to training load.
As your FTP increases, does that mean it may be difficult to increase your Fitness metric? Is it more important to focus on FTP or Fitness?
Regarding the Fitness question, I highly recommend this great guide here:
Answer in short: yes there will be some time when you can’t increase your fitness number anymore. But that doesn’t mean that you can’t progress anymore. You should use this numbers as a tool, not as a target.