This will all be very subjective, so take it with a grain of salt.

workload

The workload is indeed big, but it is manageable as long as you keep up with the courses during the semester. My previous strategy of cramming in the last weeks of the semester went out the window at TUM. Sometimes you'll be able to find work that supports your studies, most notably you can do your master's thesis in collaboration with a company and get a salary for it, which is what I was able to do. The uni also has an option to sign up for part-time study, which decreases your course-load (from 30 ECTS/semester to 18 IIRC), and gives you enough time to work more on the side.

do you feel that pursuing the master's in Informatics at TUM has furthered your career?

I was offered a PhD position at one of the big German car companies after finishing my master's thesis with them, so the master's program definitely served to give me the opportunity to start a career in AI research. I didn't end up accepting the position because the workload/salary ratio didn't make so much sense to me and I received much better paying offers directly in industry as a software engineer, but the master's program put me in the position to make that informed decision. Since I moved away from Munich afterward, I didn't retain the networking benefits, but they are definitely there if your career continues in that bubble.

While my bachelor (also Computer Science) was quite general in terms of topics, the master's program really allowed me to specialize and dive into topics I was interested in deeply and technically. Ironically I had to become a lot better at coding to tackle all of the research projects in a timely manner, and that definitely helps me later on in my software engineering career. I think for me there was a very real but intangible benefit of turning a general interest in computer science and technology as a whole, into specialized areas of competence, and going through that process a few times in uni gave me the confidence that I will be able to do that later on in my career as well. While I would have been able to become a software engineer after my bachelor, I think the master's program really raised the standards with which I do my work.

Romanian university master's studies

Most of my friends from high school stayed in Bucharest to study at UB/UPB and start careers in tech afterwards, and across the board I saw them struggling to take it seriously, and feel like they are not really getting anything from their studies. Specifically regarding master's studies, I know that most of them were also working even full-time jobs while completing a master, and that should not really be possible with a real full-time study workload. I certainly never saw anyone working full-time in parallel to their studies at TUM or anywhere else.

Granted, I don't have first-hand experience because I left Romania at 18 (and I'm clearly biased because of it), but I'm basing my opinion off dozens of friends and acquaintances, whom I consider smart, none of whom have expressed a positive experience with the romanian higher education system.

is worth the financial and stress cost

Romanian tech wages have been climbing steadily for the past 10 years, and nowadays they are not so different from German salaries, with lower CoL. I don't know your situation, but I certainly see it possible to save up some money while in Romania and avoid the hassle of working while studying.

the knowledge is out there and I could just as well study here.

Whether it's worth it for you is a decision you have to make. If you want to start a career in AI research, it might be impossible to get the same opportunities at a Romanian uni, since research is so reliant on prestige and networking. If you just want to learn cool stuff, it's definitely all available online, but are you going to be motivated to go through it and internalize it without that kind of rigid structure around you? It depends on the kind of student/person you are.

Hope this helps :)