They're not just simple configuration changes from each other
Given the individual license cost difference between IntelliJ Ultimate and the All Products Pack is minimal it’s worth it, especially given it’s cheaper than IntelliJ + CLion separately.
It also worked out well for me because I bought Ultimate on sale, and the suite was discounted for existing owners. So it's really been good savings. Regardless, given the time savings the IDEs give me, they pay themselves off pretty quickly.
So either [1] you buy IntelliJ Ultimate & get Java + other languages (PHP, Python, Ruby, etc except .NET and C++)
or [2] you buy the language specific IDE (cheaper) like PhpStorm, PyCharm, etc
However, if you used the paid IDEA, adding the Python plugin gave you full PyCharm capabilities EXCEPT that IDEA was always based on version N of the core IDE platform where PyCharm was based on N+1 version, i.e. the smaller pycharm IDE sometimes had some newer platform features than the IDEA ide which led to occasional differences between IDEA + Python plugin vs PyCharm.
I switched to VSCode last year and let my licence lapse for Intellij so things may have changed.
What i will say, despite having moved to VSCode and being entirely happy - Intellij is the better platform. It’s the difference between 80% and 99% though, and the VSCode 80% is good enough. If i went back to full time dev, i would buy another jetbrains licence.