Hi Shibli,
Without the wider context it is difficult to know exactly what the differences in meaning are, but in general, sentence one describes an action in progress at a specific future time e.g., I'll be waiting for you outside the cinema at 7.30pm. We sometimes use future continuous to describe something that happens as a result of an arrangement or a normal routine e.g., Speaker A: After the plane lands, I''l be waiting for you in the arrivals lounge (used as an arrangement) or Speaker A: What are you doing tonight? Speaker B: I'll be training at the gym (= I always train at the gym; it's my normal routine).
Sentence two is probably just future simple used to express a decision made at the moment of speaking e.g., Speaker A: I'll pick you up after work. Speaker B: OK. I'll wait for you outside. See you later.
Hope this helps.
Thanks,
Maria
