I have a Kent Nazz gravel bicycle. I am planning on making it a project bike to learn with. But I also really like the bike and how it feels. I got a Poseidon X also and I actually like the ride of the Nazz better, probably because I'm mostly riding on bumpy side walks. I want to replace the rear derailleur and potentially bottom bracket, crankset and chain.
I've looked on the Shimano website and seen many options for rear derailleur. The current derailleur on the bike is what I have seen on line referred to as a Shimano flatface. I have had no issues with it but I want to know if a new slightly better entry level part would provide a better ride along with some of the other planned changes.
I am looking into the Tourney TX line for example as they seem slightly better. Should I simply look for a model that is a fit for a 2x7 drivetrain? I know there are long, medium and short cages. What should I select as far as this goes? Is there something else that I should consider?
As far as the crankset and BB I keep reading and hearing that these components are the least important in an upgrade. Why is that, given that they are a part of the drivetrain? I was looking into this crankset: https://bike.shimano.com/en-EU/product/component/tourney-a070/FC-A070.html And for bottom bracket: SHIMANO Square Type Bicycle Bottom Bracket - BSA 68MM, Spindle: 127.5MM (D-EL) - EBBUN300B27B