It depends on the individual, but wholistically, it’s not too time-consuming, as many students participate in Greek Life, do well in academics, and are involved in other places on campus. Is it time-consuming? Yes, it is a commitment. Is it too time-consuming for you? Well, I don’t know you…. so I can’t say.
Are “the Greeks” strict? Well, I’ve never heard of anything like the example about your friend being fined for missing a social event at RPI. Getting involved in Greek Life is meant to build your character in many dimensions (personally, socially, professionally, academically, etc.). You should attend rush events in the fall and ask these questions of the Greek students.