You will need to keep the looper as the Kemper looper os more of a toy really. It is great for auditioning profiles and for sending a phrase to an amp when setting up mic positions for making new profiles but it is pretty limited as a live tool.
I don’t use any other pedals with my Kemper toaster though. I have an old pedal board with a Strymon Mobius and Timeline aling with a TC Hall of Fame reverb, Fulltone Full-Drive 2, a fuzz, MXR Distortion, Cali 76 Compressor, Whammy DT and Dunlop Wah. All controlled from an RJM Mastermind PBC. However, I haven’t even taken the lid off the case in well over a year now.
Rather than taking anyone else's advice about pedals, i would strongly recommend doing a simple A/B test with each of your existing pedals against the Kemper FX. If you can get as good a sound or close to as good for your own ears then make your life easier and ditch the external pedal. You will be pleasantly surprised by the Kemper Delays and Reverbs. The OD might not be right for you but in my case they are close enough that simplicity outweighs any marginal tonal difference. The Kemper Wah and Transpose Pedal are easily as good as my Dunlop and Whammy to my ears bit many others feel strongly the other way so make your own mind up.
The only pedal from my old rig that I miss is the Cali 76 Compressor as the Kemper Compressor is OK but doesn’t introduce the unique character of something like the Cali 76. The Kemper is more transparent
If thats what you want then the Kemper compressor is good enough to not ned an external pedal either.