Mac vs. PC
In terms of the whole Mac vs. PC debate I am not going to attempt to convince/convert anyone one way or the other-- suffice it to say if you are cutting on FCPX you NEED to have a Mac as Final Cut Pro is not supported on PCs. As far as where you buy your Mac from I can only recommend to buy directly from Apple or else keep your eyes open during various sale seasons for $100-$300 off of certain Macs at places like B&H Photo and Adorama in NYC. Beware of 3rd party/refurbished type deals that seem too good to be true-- they often are. Whatever you do just make sure you are getting the manufaturer's warranty along with the purchase.
For official minimum system requirements for FCPX you can check that out here.
In terms of being able to handle 4K video natively (or 6K or 8K etc.) it has just as much to do with your hard-drive speed and the type of connectivity to your computer as it does the CPU, GPU or RAM so don't put all your eggs into those baskets. For instance, you could do better getting a weaker MacBook Pro that has USB-C /Thunderbolt 3 than a faster MacBook Pro that still only has USB 3.0/Thunderbolt 2 connectivity-- depending on your storage solution.
Feel free to scroll down below to find some recommended hard drives and storage solutions.
Size Matters (MacBook Pro):
The last thing I will say is that if you are going the MacBook Pro route (rather than an iMac, iMac Pro or Mac Pro) for your editing you need to make sure you get the 15" model. This is not a vanity thing but rather the 13" MacBook Pros do not have a dedicated graphics cards in the same way the 15" models do-- so they really are different computers altogether (and not just different screen sizes).
If you want more help choosing which Mac is right for you head over to one of my favorite YouTube channels for in-depth, accurate and tech-minded reviews and comparisons of Mac (and other) products: Zone Of Tech.
Aside from the computer itself your hard drives are going to be the next biggest determining factor in terms of speed and reliability of your editing system. As touched upon earlier most folks these days are still rocking USB 3.0 and Thunderbolt 2 connections (mini-display port interface)-- though the USB-C/Thunderbolt 3 capable ports are slowly becoming ubiquitous-- not just on computers but on most electronic devices (like tablets and smart-phones). Since some USB-C drives come with USB-A adapters-- or you could buy one relatively cheap-- I recommend going USB-C when you can even if you don't have the port on your current set-up. It's just a nice way to "future-proof" your equipment if you have the money to spare.
I've also included a few SSDs (Solid State Drive) recommendations as well as some popular RAIDs for your bigger/faster needs.
SSD/USB 3.1 HHD/USB 3.0 HHD/TB 2.0 SSD/USB-C RAID/TB 3.0 RAID/TB 3.0
Since hardware-- especially connectors, plugs, ports and cables-- changes so rapidly these days you may find that you end up re-buying certain things every two years or so. This is slightly unavoidable of course if you want to stay up to par with the speed of tech (see Moore's Law)-- but one way to mitigate this is by investing in a quality USB hub to expand the connectivity of your computer both by quantity and type. Now you will only ever go as fast as the port on your computer itself (for instance, a USB-C hard drive plugged into a hub that is connected to your computer via a USB 3.0 cable will still only be as fast as the USB 3.0 connector-- and not utilize the full potential speed of the USB-C drive itself. Below are some hub recommendations in various different price ranges and functionalities/abilities.
USB 3.0 Thunderbolt 2.0 USB-C/TB 3.0
Whether you are an editor who likes to use their keyboard shortcuts, one who prefers to have their hand on a mouse most of the time, someone who loves the precision of a tablet-- or a combo of various options-- I do recommend at the very least upgrading from the Apple keyboard and mouse that comes along with your computer. They may be sufficient for everyday tasks-- but they are not optimal for long hours of editing work-- especially Apple's mouse.
A lot of editors like to either utilize some sort of macro-button panel or a gaming keyboard/mouse in order to widen what can be done via shortcuts in programs like Final Cut Pro. Below are some popular options for such things.
MOUSE MOUSE KEYBOARD CONTROLLER CONTROLLER TABLET
As far as monitoring your video-- if you want to do accurate color grading that is-- you will need to not only get a monitor that is capable of being finely calibrated but also the proper hardware output from your computer (and a probe to calibrate the monitor if it doesn't have internal calibration). If you just need a decent monitor for editing and/or other type of non-color specific work you have more options. I also like the ultra-wide monitors as a working monitor for your timeline and bins. The extra real-estate really pays off when working on your timeline/sequence.
Similarly to video monitoring, what you get for your audio monitoring will all depend on the nature of your work. Are you just doing offline edits and handing them off to a professional sound team/facility? Or are you legitiamtely trying to do serious sound design/mixing at home? If so you need to spring for a nice pair of studio monitors and a pre-amp of some kind to interface with your computer. Below are some recomendations for affordable studio monitors as well as the Focusrite Scarlett (a very popular audio interface that gives you balanced/XLR outputs). And although I don't recommend doing final mixes with headphones I have included here my recommendation for studio headphones-- as these AudioTechnica's are the best headphones I've ever worn.
Below are some furniture suggestions for your edit suite that I highly recommend both in terms of quality and affordability. The VIVO TV CART can handle a LOT of weight, the HALTER STANDING DESK is just as solid as the more recognizable/expensive brands; the LANGRIA Laptop Table is a solid/versatile choice for anyone who needs a portable table-top in their suite and of course you can never go wrong with a quality mouse-pad with a wrist-rest.