Tighter fitting tubing is actually likely to cause you more issues. It's a myth that capricorn tubing is better in any way. In a way, you want a somewhat loose fitting tubing; especially if you're cheaping out on PLA.
So, say you've got a partial clog -- The thing that usually happens is the feeder will skip/slip or tear into your filament. This causes the filament to go out of round, and can even push the sides of the filament out further than the tubing is wide. This causes the filament to then take more pressure to push through the tubing, adding to the already existing problem.
It’s a myth that capricorn tubing is better in any way
I'd call it "successful marketing" :) But yeah, they're really managed to convince a lot of people that it has near magical properties, and I've seen a lot of random people recommend it to others for all sorts of issues.
With direct drive, I would say it doesn't make a difference.
For bowden there is a benefit.
I also think that direct drive is superior to Bowden setups in nearly every situation. The current generation like the Orbiter v3 is a very light direct-drive extruder.
There is not. I can empirically prove it to you as well. Half of the 'capricorn' tubing you get from Amazon isn't even genuine - yet everyone there is clamoring on about how it made a difference.
Turns out, that confirmation bias and placebo effect share a lot of overlap. I get it, nobody wants to admit they've been bamboozled. But hey...stay critical of your observations.
Go the other way and buy 3mm tubing and see what it does :)
Fair enough bowden has a lot of issues like filament compression (which can't be fixed with tubing) making it difficult to maintain a steady flow when conditions aren't steady (e.g. acceleration and so on).
With larger diameter tubes the issue of filament compressing gets worse. In a nutshell, a larger tube diameter for "rigid" materials somewhat is similar to the effect of a softer filament/material.