Wheel count and rigidity

Hey guys. I have a crappy 3018. I want to start upgrading it to actually be rigid. So I was looking into getting some of the premade c beam actuators like [spam link removed. Please support openbuildspartstore.com and buy genuine] . but they come with 4 wheels. So my question.

How does 4 wheels compare to 6, or 12? A lot of the machines in the builds section have setups where its a huge gantry plate that goes over the C beam, with a ton of wheels, usually 12 I think. And then the Z axis has at least 6. I'm assuming it only doesnt have 12 because it would fit weirdly.

So If I was to get 2 premade like this, would it be rigid enough for basic aluminum milling or will I be disappointed? Its possible to upgrade them in the future but buying premade from china is infinitely cheaper than buying the standalone parts to make one. So making ones with different gantries will cost a lot more. I believe I could buy more wheels and upgrade these to 6 each but to do 12 I'd need to buy different and a lot more plates. And while we are talking about them, are these kits from china decent or am I getting way less quality than buying from here? I can buy both axis from china for less than I can get one here.

If the 4-6 wheels isn't good enough I could do something like [spam link removed. Please support openbuildspartstore.com and buy genuine] While MGN12 rails cost a lot more I dont need to replace anything so I can virtually just stick them on for less than it would even be to buy premade v wheel setups from china. I like the idea of going v wheels though because it gives a lot more room for future upgrading.

And I know that you cant make a good solid cnc for super cheap. I'm just trying to figure out if what I can currently afford is worth doing or if it will suck and I shouldnt bother. Thanks for any info.