For speed no one can give you a concrete answer
because it depends on the complexity of your website and all the external resources it uses including third parties, it also depends on whether dynamic or static content is being served at that moment, Cloudflare or not, optimized images as well as code or not, the platform on which your site is based and so on.
In general for free service the speed is more than satisfactory.
Bandwidth is unlimited,
but there are some other things that fall into Fair Usage Limits, so please read the whole that section (in left menu).
Some huge outage hasn’t happened in a long time,
mostly there are cases on a small scale where one IP out of a hundred is attacked by DDoS
and then that IP must be shut down to protect the server until the attack subsides.
And from time to time some works can be expected on a certain cluster/volume/DB Server/ in the form of service improvements (new hardware, increase in speed, security, etc.)
because it is clear to you that whenever some software has a security flaw it is a good practice to install the patch as soon as possible… and then, depending on the complexity of the task it just required some time when “something” has to be offline until the end of that process.
The service is free and it is unrealistic to expect superior performance, and other parameters as opposed to using a paid service, so it is essential to adjust the expectations a bit.
The vast majority of people are satisfied
If I can suggest something to you ( because I see you are worried)
So, instead of moving the domain here, before that… you can use one of the free subdomains
and migrate your files and DB there
This procedure will also let you know what changes and settings you need to change in order for your DB to adapt to our DB server or any other action…
Also, you will have time to adapt to the new environment (host)
at the same time you can track speed and everything else for a few days
and then if you are satisfied you can then also move the main (LIVE) domain here