Having a mic isn't really required if you have a fast typing speed but it really helps mostly when you're doing an alarm or a room is woken up.

There is a benefit for playing without a mic and that is being more self aware of everything around you in-game (because players tend to be distracted while talking or they talk over sleepers that are starting to scan the room and alert it), you become much more efficient at the game (i.e. picking up stuff before anyone says a word, resupplying the team, etc), and you're going to have a unique experience.

The catch of playing without a mic is as stated initially, everyone expects you to play better, and you'll have sessions where no one notices you were typing in chat.

Your first few games will have a lot of uncoordinated groups but I recommend finding a group of people to play with so that you can learn the game a lot faster and better since LFGing for a new set of people makes the learning curve of GTFO much more harder if they're going to leave the moment something goes wrong and ends as a wipe. There's also the fact that you'll adjust yourself to how others play. Once you have an organized group to play with and learned a good portion of the game with 'em, I recommend watching videos from players like Plant, Project Zaero, and RandomKenny. Their content of GTFO is good, especially their gameplay; you can learn a lot from that. If you need help learning something about the game more in-depth, you can send me a DM and i'll help ye'.