@Minecraft1 

You have the option of a hardware controller OC200/OC300 or installing the controller software on a laptop, VM, Raspberry Pi etc.  I would not recommend purchasing the OC200 as it is now woefully underpowered for the current version of Controller (5.14 at writing) and the OC300's days are numbered too in my opinion.  You can download the Windows or Linux controller bundles from the Support site.  I run controllers in VM's on a NAS and on Pi Clones as you need them up 24/7 to retain mesh auto functions or to recover in the event of power or signal interruptions.  TPlink also offers subscriptions for Cloud based controllers too (but they require active internet access and are not the best option for private networks or where internet stability is poor).

My suggestion is that you try the software controller first as it is free and see if the devices perform as you need them to first, before committing to hardware.

As for hardware, I would lean towards a Pi5 equivalent with at least 4GB of RAM, though you can get away with Pi4's and Clones with lesser CPUs if take the Docker approach (though you will still need 4GB of memory to support recent controllers). 

I wish TPlink would modularize the controller as there's a lot of stuff in there I don't need or use, but the have been very quiet on the software update front for the last year or so.