Road Tubeless Sealant Needs the same as MTB needs?

I use Stans Race, because at over 90kg my tyres run at higher pressures than most, I frequently ride off-road/gravel and I fear I am somewhat of a "puncture magnet"  

I previously tried ordinary Stans and Effetto Mariposa Caffelatex. Both regularly coated me and bike in clouds of latex before leaving me with a sticky mess and the joy of a road side re-tubing.

Stans Race is not perfect, it's a pain to add, over time it makes a clumpy mess inside the tyre, I have occasionally needed to fart about topping up with extra air, coaxing the sealant into hole and once, adding a plug. But in the two years I've been using, first in the Grade and now in the Hakka's tyres, I have always been able to complete the ride without having to tube.

I haven't had the best experience with road tubeless (have been using MTB tubeless for sixteen years though). I agree that a lot of sealant is lost regardless of position of cut, and it is cuts, rather than thorn type punctures, that pose the biggest challenge due to the high pressure and small size of the rubber. I long for the day when self-healing polymers are used in tyres.

Muc-Off No Puncture sealant gets excellent reviews, even at high pressures. It's pricey. I like that the littel pouches it comes in attach directly to your valve and you just sqeeze the stuff in (need to remove valve core of course).

Not all sealant is created equal. I tried stans usual mtb sealant with road tubeless a couple of years ago.. it was totally useless. Just would not seal at anything above 60psi.

Conti Revo is also useless.

Orange Seal works, however I use Bontrager TLR Sealant which I find the best sealing (although you do need to shake the bottle a lot before use).

The only sidewall cut I've ever had was last year about 14miles into HONC. That was offroad crazyness, I was running 33mm tubeless schwable g-ones at around 35psi - annoyingly I had to catch the broomwagon back to base.

Never had a side wall cut.  Ive had bad cuts on the tread that havent sealed instantly, but allowed me to continue slowly.  In those cases I've fitted a tube when I get home, injected 70mil of selant into innertube.   Job done, infact Ive never had to change a tube with selant for years

This is the issue with road tubeless, the high pressures mean the sealant often gets shat out before it can do anything. Are you using regular Stans? You might want to try the Stans Race, but beware trying to inject it into the valve as it tends to clog up that way - you have to pour it into the tyre ideally. Some people swear by Orange Seal.

Or go without sealant and if you flat, use some Tufo Extreme. I use that in my tubs in a pinch, strong sealant but it won’t last long in the tyre 

Sidewall cuts are tricky to deal with when it comes to tubeless. Thats prb the one drawback, as the size and location of the damage makes it difficult for the sealant to do its job. In the case of a bigger sidewall slash, you need to remove the wheel, shake the sealant toward the hole by waggling and angling the wheel, then reinflate. Then repeat. Be prepared to do it a few times. And yes, quite often the pressures are too high for the sealant plug to cope, and it just blows again. Thats just how it is, overall tubeless is more puncture proof but certain cases are not its strong point.

I'm not an experienced cyclist, but in 30k miles of road riding I've never had a sidewall cut.