They have differing levels of formality and both are a little strange. We need to meet /before lunch/today/this week. (Using something vague like ‘urgently’ ironically makes it sound less urgent!) ‘Meeting up’ is usually less formal and less urgent. Let’s meet up for lunch (sometime).

Hi no, both are not the same. They slightly differ, the first one suggests a casual and informal tone, whilst the second suggests a more serious tone.

We gotta meet up real quick. - the meeting is "real quick" or for a short amount of time. This would normally be something that takes place right now, but could be scheduled. It would be better to say "we need to meet real quick", but "we gotta meet real quick" would be ok in a really informal setting since "gotta" is not a proper word. We need to meet up urgently. - Means that it is very important, but has no implication of exactly when or for how long. Although, soon would be implied since it's urgent. This sentence is poorly formed.