I have never taken a proper IQ test before and I am genuinely curious what the experience is like. Do you just sit down and answer questions or is there more to it than that? I also want to know what kinds of tasks are actually on a real IQ test because I have only ever seen the matrix puzzle type questions and I assume there is more to it than that.
A proper IQ test looks nothing like the quizzes you find online and honestly the difference is pretty striking 
A full clinical assessment like the WAIS covers multiple distinct ability domains including verbal comprehension, perceptual reasoning, working memory, and processing speed. You might be asked to define vocabulary words, repeat sequences of numbers forwards and backwards, arrange blocks to match a pattern, identify missing elements in images, and solve matrix puzzles under time pressure. The whole thing takes anywhere from 60 to 90 minutes minimum because you need enough task variety to estimate g reliably across domains. Online options with real psychometric foundations follow a similar logic. RIOT IQ for example covers 15 subtests across 6 CHC cognitive domains which gives you both a general score and a detailed profile of where your specific strengths and weaknesses actually sit 
That subtest level breakdown is honestly the most useful part because two people with the same overall score can have very different cognitive profiles underneath it.
The number of subtests is usually a good signal of legitimacy 
If a test has 5 questions and takes 3 minutes it is not measuring your intelligence, it is measuring your willingness to share something flattering on social media. Real assessment is longer and more varied than most people expect.