It sounds like your budget is too low to try to do everything you want to.

Supporting one control panel alone is a lot of work never mind two or three of them, unless you have a big team behind you, which you don't.

I would say focus on the control panel you are most familiar with cPanel.

You may need to stick to reseller hosting with your budget. Maybe look into switching from reseller hosting to running your own managed VPS/Dedicated servers to offer Shared/Reseller hosting to start with. The next step would be to use unmanaged VPS/Dedicated servers from a provider like Hetzner. Then from there, you could resell VPS. Finally, set up your own VPS node to reduce overheads and later start reselling dedicated servers.

There is not much to be made when reselling dedicated servers. Better if you colocate your own hardware as better profits etc.

If it is mainly you probably best to stay small, slow-growth.