Setup highly available/redundant (multi-server) dynamic one-site hosting with whole server backups?

Hello, I need your precious advice on how to proceed with a dynamic website (PHP8+MySQL5.7+Redis+supervisor, rsync) hosting as a newbie in webservers management.

Virtualmin - Webmin
I am assuming that my control panel of choice would be Virtualmin (which is said by 3rd parties to be a module of a Webmin) and inside Virtualmin I will still have some general server monitoring functions like it is in Webmin (per the screenshots - i am not user of it) since Webmin is installed along with a Virtualmin (per this comment).

High availability (load balancing) or failover for a single site:
After setting up the webserver and hosting a dynamic PHP+MySQL site, some time passed, I see that i need load balancing or want more redundancy (fail-over to a secondary server) can i setup this via Virtualmin GUI or can you link me to a CLI tutorial? And is it really handy to setup this high availability (multi-server setup) right at the beginning instead of after one year of a single server hosting?

Backups:
In case I will end up on a single server setup, then i would want to backup all the data on the server (i mean ideally all data on drive) from time to time so it can be easily recovered with a different server provider and then backup the website data more frequently off the server. Is this possible via GUI? How? Or do you suggest any third party tutorial?

If you are not willing to link to article/tutorial, please kindly mention exact feature names so i can try to find the tutorial online.

I have already read High Availabilty, Virtualmin with Multiple Servers - #4 by Joe (not layman detailed, no GUI setup)

Well virtualmin installs MariaDB version 10

That’s a bit old maybe, if your going to use mysql, use a later version if I remember correctly that is version 8.x

There are some steps on how to replace MariaDB by MySQL:

Though such replacement may cause issues as mentioned on same page under later post:

Another replacement steps:

https://blogs.oracle.com/mysql/post/how-to-migrate-from-mariadb-to-mysql-80 <<<<

It is worrisome for a layman needing to manually switch from MDB to MSQ. I am already having established site with populated database 10.6.18-MariaDB-cll-lve . My script provider is using MySQL, but told me i may stay on a MariaDB. So that may not be a big problem.

Can anyone please address the main questions in the 1st post of this thread regarding clustering/high availability? I would like to stay away from a load balancing setup with single load balancer (a signle point of a failure) and I think I would need a tutorial. Thank you in advance.