starting a shared web hosting business

i want to buy a hetzner dedicated server and start reselling it
the server specs will be
AMD Ryzen™ 9 7950X3D
128 GB DDR5 ECC
4x 1.92 TB NVMe SSD (Gen4)
so i calculated that in the worst case scenario if all my clients buy the smallest plan i offer which will be around 4 GB of space, i will have around 900 client/website. (I know 4gb space isn't alot but i'm based in the middle east and my client base isn't that tech-savvy)
my question is, can a server with these specs handle this number of clients/websites and if not what setup should handle this?
also i've been looking for a decent webhosting panel and i can't choose between Cpanel and Spanel
cpanel regardless of the unstable pricing, it will be a cheaper option for me since i'll be able to get a discounted price considring the amount of licenses i'll buy.
on the other hand spanel seems like a better option for me since they'll manage the server for me and offer support to my clients so i don't have to worry about the support part from my end. but idk if spanel can handle this number of websites without the stability and security features in cpanel+ cloudlinux like cagefs
sorry if i misunderstood anything i've been researching for a while and trying to understand this business more

This depends on how heavy are the websites, usually such server config can handle even more than 900 websites easily, but again, it depends on how much traffic are per website.
On the other hand, hetzner is really strick with abuses, from time to time if there is any serious abuse, they completely suspend your server and or account termination, in which it will cause you alof of troubles. I would rather pick more servers with lower config and price in which you can split the cpu/disk write/read/traffic in multiple servers instead of putting all in one basked/server in which it will degrade performance.
As per cpanel and spanel, from my experience, 90% of customers know/prefer only whm cpanel as a panel, and other panels are not preferred. Spanel is really similar to whm cpanel but still it's another platform. Apart from tech support, you can still hire outsource support alot of companies around doing that. At the end of the day, you are the one who have to decide, but my advice is not to put all eggs in one basked.

The Hetzner dedicated server you're considering, with its AMD Ryzen™ 9 7950X3D, 128 GB DDR5 ECC RAM, and 4x 1.92 TB NVMe SSDs, is quite powerful and should theoretically handle around 900 clients with small websites (4 GB each). However, the actual capacity can vary significantly based on the nature of the websites (static vs. dynamic, traffic volume, etc.) and the additional resources needed for the operating system, control panel software, databases, and backups. Between cPanel and SPanel, cPanel is widely recognized and might be more economical, but it requires more hands-on management. On the other hand, SPanel offers server management and client support, which can ease your workload, especially if you're new to this business. Ultimately, your choice should consider both the technical capabilities of each panel and your comfort with server management and customer support. I found this dedicated server hosting online; you can also check this. This might help you. Hope this will help you.

As already mentioned, the server could easily host 900 clients/websites... and it also just as easily couldn't. There are too many factors to take into account, you sure can host 900 low utilised websites but 900 high traffic websites? You're going to struggle.

There are a numbers of ways to ensure resource is utilised better, such as using Litespeed as a web server and ensuring your MySQL/MariaDB instance is highly tuned. Previously I've worked on projects where the business needed the most, bleeding edge performance possible out of every server so I'm highly experienced in tuning the Linux kernel for various use cases, so there's that you could look at too.

To be on the safe side make the lowest plan bigger to ensure less clients/websites crowding the server which means less load, more stability and better overall experience for your clients (the price will be higher though which won't appeal to all clients), also consider investing in LiteSpeed webserver which will enhance web hosting tremendously and handle load properly (can be expensive) and other software like cPanel (also expensive), DirectAdmin (Way more maintainable), Cloudlinux, JetBackup and e-mail channels/tunnels (you and your clients will probably be having a better time with them)