The RPM package is signed with my key, and it looks like you don't have my public key.
My public key should be available on key servers for example Open PGP listed under my email.
Crystal Remix, in the most recent versions, uses mostly Crystal Project icons because I also think it's the best one out of the three, and also for consistency reason like you said. I will update the project description to reflect this. I will also try to increase the coverage when possible.
It's not a coincidence that Crystal Dock is similar to KoolDock -- they are both based on my previous dock KSmoothDock which I wrote for KDE3 and KDE Plasma 5. KoolDock was a fork of it during KDE3 time, and Crystal Dock is the successor dock. I changed the name mainly to reflect the change from a KDE-only dock to a cross-desktop KDE-first one.
Hi, yes you can right-click on the clock to show the clock's context menu, then Font Size -> Small Font / Medium Font / Large Font.
The default is Large Font so if you select Small Font or Medium Font it will be smaller.
It's all about the look - One prefers a taskbar or another mainly due to the look :)