I am brand new to the world of Kemper products, and digital rigs and pedalboards as well.
Hi, welcome and have fun here in the forum and with your Kemper!
Kemper has improved the effects in the Profiler over time via updates of the firmware and many people incl. myself refer to them as rather outstanding. Maybe with some small drawbacks here and there and surely depending on where you come from and what your expactations are. It will take quite some time until you are through all the different effects - don't get misleaded by a few profiles which come with a limited spectrum or parameter settings which do not suit your needs. You can change all this. Take your time, watch the YouTube stuff and learn how to tweak it. It's worth it
And naturally you can use analog effects together with your Kemper. Personally I try to avoid this due to the quality of the built in stuff but still own a wah pedal and a tube screamer which I still use with the Kemper. If you put effects in the loop then yes, the quality might be impacted by another DA/AD conversion. I think for live use it doesn't matter, in the studio I would think about it. Just my two cents.
My advice: Don't give up too early. The reputation of the Kemper stuff has a reason. And maybe let the audience here know a bit about the sound you are aiming at. Many people here know great tips and tricks how to get there.