You are correct that it is present perfect continuous. When you use "lately," you don't need to specify a time frame. "Lately" just means in the recent past, and is usually used with a habitual action. Ex. I have been studying a lot lately - means that recently you have studied on multiple separate occasions. Let me know if you want any further clarification.

One of the uses of the present perfect is when you are talking about something before now and that exact time in the past is not important. "I have travelled a lot" is one example using your example. Your travel is in the past (before now), but the exact specific time of that travel in the past is not important. Maybe it was a lot a week ago, maybe it was a lot a year ago, etc. When you use the continuous tense, you want to give the listener a sense that this 'event' went on for a period of time - it had a duration. It wasn't something that happened quick and then was over. Using your example again, "I have been travelling a lot lately." gives a sense of the time duration of this travelling in the past. The listener can visualise you travelling over a period of time, and not just an instant in time. 'lately' is not necessary for the present perfect continuous. It's just used as a time market to tell the listener that this travelling was recent and not further back in time.