たしかに= Certainly (used when you agree with somebody)
もちろん= Of course (used to strongly agree with somebody, much stronger and definite)
can use mochiron by itself too, もちろん!! of course!!!
Maybe you can for tashikani too but it's not as commonly used by itself, it's like "I certainly agree with what you said, but ___ (and then say a different view" You can do the same with mochiron too though so they are similar, but just mochiron is stronger overall.