How much traffic per month does it cover in this amount?

I want to launch some toy projects and confuses whether go for AWS or vps.

20 TB.

I would definitely recommend going with a VPS over AWS in your case, unless you want to play with AWS-specific tech to build up your resume.

are you also installing the DB within the VPS?

I would be needing a web app connecting with MySQL and a bunch of Crons.

Also, could I host multiple domains?

I don't use a DB. But sure, you could run both your app and the DB on a single VPS.

Yes, you can host multiple domains. You can either point multiple domains to a single IP of your VPS, and configure your web server to use name-based virtual hosting, or you could buy an extra floating IP, assign it to your VM, and use IP-based virtual hosting.

Is it done by hosting guys or I have to do on my own? Also what about backup? I am not quite good at devops/admin stuff hence asking

You have to do it yourself. But it's not that hard. The easiest way of hosting multiple sites is probably to just assign multiple IPs to a single VM and simply run multiple servers simultaneously, each listening only on a single IP.

As far as the backup is concerned, Hetzner has the option of handling it for you for 20% extra money.

In my opinion this question seems like a good reason to get your feet wet just a bit. Just gaining some understanding of how things work under the hood is worth it even if you end up never using it professionally.

The basics of operating a (virtual) server to run your apps on could be seen as similar to learning the basics of cooking food. You can eat fairly well for the rest of your life without knowing a thing about it but if you just spend a single hour every week preparing your own food, you will become more familiar with the food itself. You would larn what individual flavors you prefer and where they come from, and you'll even be able to survive on less money if you would need to, or even survive more easily in a potential crisis where home delivery isn't an option.

If you spend an hour every week to learn some system administration (what people call "ops" nowadays) you'll be able to realize when you're being overcharged for simple services, feel the power of building a larger part of your stack yourself, play with new things, etc. Running multiple apps on a single host with proper backups is a trivial problem, especially if you know how to code, and in my opinion these things shouldn't be "left to the devops team" or seen as "IT stuff".

Not that long ago most developers had to know what environment their software ran in as part of their job, and despite many attempts to move away from it, this is still mostly true even if we have switched from the Linux CLI to cloud dashboards, CI/CD pipelines and Terraform scripts...

I am currently using a bunch of AWS technologies, e.g. AWS EBS, RDS etc. I am also thinking to consolidate all projects to a single AWS LightSail, which offers pretty cheap instances, e.g. 512 Mb, 1vCPU, 20Gb SSD for 3.5$/month.

20 TB of outgoing traffic is included with a Hetzner Cloud VPS, any additional TB costs 1,19€. Incoming traffic is free.

what benchmarks do you use? I'm curious how my VPSes compare.

It was quite some time ago so I don't remember exactly, but I've basically used one of the usual benchmarks that everyone uses to measure the number of requests per second that a server can sustain.

(I've rented another VPS in the same data center and ran the benchmark from there.)