Reaper is very menu heavy, but has a good amount of keys bound to actions. Check the key bindings list and try to memorize them, much like you probably have done for other things given your setup.

To be honest, when I tried using it forever ago I got lost and gave up. I forced myself to use it because I liked the feature set, but moving over from FL was very difficult for me.

It took time, but I've figured it out enough to where I can't imagine using anything else.