I am trying to understand which cassettes I can install on my bike. I've understood that the length of the derailleur also determines which cassettes will fit.
In my case I have a triple (see picture below), with a 10-speed cassette, in the range 12-25. My experience with this cassette (and 30-tooth chainring) in the 18% stretches is not too pleasant. Therefore I am looking for options to replace it with a cassette with sprockets up to 27 or even 30 tooth.
My main question is how I can determine which cassettes will fit on my bike. Even more I would appreciate a general answer, that explains what the limitations are of the derailleur when choosing cassettes, such that I can determine it myself.