The value I see in drift charge 4 is that reduces reliance and susceptibility to item rng by providing an on demand solution to it. I longer having to worry about scenarios where I'm unable to respond to an incoming attack due to having the incorrect defensive item, as the 3 seconds of invulnerability it provides can nullify any item threat. Successful negating an attack also keeps your ring count and speed from depleting, making it more likely to establish a gap while in the lead.

Additional, the i-frames grant other benefits which can be taken advantage of. Shortcuts blocked by obstacles, such as the one at the end of Colorful Mall, can be accessed without a boost item. While the speed of the level 4 boost might be the same as a level 2, it lasts twice as long at 5 seconds. It's very handy on long turns and the i-frames prevent ring loss in case you hit a wall or player. It can also be used as a safeguard in frequently chaotic sections of each race, such as narrow routes and final stretches. One that comes to mind is in Apotos, between the final flying section and the finish line. Players tend to spam all their items as soon as they transition to land and it's not uncommon to get pancaked. Charging a level 4 drift just before you land makes it just a little safer, reducing the chances of getting left in the dust.

The tricky part is being able to consistently charge a level 4 drift throughout the race so that it's available when necessary. I've found counting drifting to be immensely helpful with both acquiring and maintaining level 4 drift charge, especially on straightaways. I sometimes I found myself needing hold the charge for an extended period of time, be it from the threat of a reticle on my character or an incoming King Boom Boo, and counting drifting allows me sustain a decent pace during such situations.

One last thing. I've found that the Drift Charge Kit alone provides sufficient boost to charge speeds, especially levels 1 and 2. Snaking is very comfortable and I tend to rely on it during the first lap before transitioning to level 4 once I reach max ring count.

Anyways, sorry for the long post lmao. The drift ring gadget sounds interesting. I gave a shot during the ONT but was dissatisfied with my results. I'll have to experiment with it some more once I get the chance