Better to be fast and make mistakes or go slow with no flaw(s)?

You're going to always have flaws, prefer to get live feedback from real users, and continue to iterate based off of feedback. There will be plenty of time to slow down later after you have a stable version out in the wild. But in general especially when dealing with outside investors, they don't want to wait to hear you have a perfect product, they want it out there as fast as possible to try and get validation for the idea, this also helps them know if they return for future rounds or if they sit and wait. There's a time and place for "slow and steady", its usually not at the beginning.

There would always be flaws whether you go fast or slow. Personally, I think it much better when you create roadmap and try as much to meet your time lines. Anything otherwise is just outside noise. Avoid it!

I generally go with the second option of going slow to ensure there are hardly any flaws, however, you need to consider the trade-offs and prioritize accordingly. The optimal balance between speed and accuracy depends on the costs and benefits of each dimension. For example, if the task involves high stakes or severe consequences for errors, then accuracy might be more important than speed. On the other hand, if the task is time-sensitive or has low impact for mistakes, then speed might be more important than accuracy. If an individual tries to perform a task faster, the quality of the performance tends to decrease, and vice versa

I don't know much but Mark Zuckerberg said in a guest CS50 lecture it is better to make mistakes than to dot everything perfectly. But yes, planning is very important too.

It is impossible without mistakes and there is no need to strive for this. Learn from them. The main thing is to do so that they are not fatal.

Yep, what @dsarkar said :) !

I'd definitely try to find the sweet spot in between. No extreme is good either way!

There will always be a flaw at some point, but it's better to be fully focused when accomplishing a task. Still, 'slowly but surely' is still a good idea, however you will always have to consider other factors. We tend to compromise the quality of the outcome when we rush things and get things done faster, on the other hand, it doesn't really guarantee that there will be no mistakes committed when it's taking so long. I guess it all boils down to balance and consideration of everything that relates to a specific task.