as for the pressure. putting low pressure in the shock results in a lot of sag. then leads to more bottoming out and less small bump compliance since youre already riding in 40% or more of the shocks travel. im 155 pounds with gear and i run my psi at 165 and my faith sits at 30%sag exactly. i do add a little more psi so it sits roughly around the 25% mark for more rough trails or trails with chatterbumps and washboard sections because the shock will feel more harsh in chatter sections if your riding too low in the travel due to the natural progressive rate of an air shock. havent had a problem with big hits on the shock though. soaks up all the hits no problem. i barley bottom out
keep in mind vivid air was designed mainly for DH racing and it has its advantages and disadvantages just like how coil has its advantages and disadvantages
read reviews of the shock, the only setback it has from regular coil as people say is small bump compliance, if you're really racing the shock provides more control then a coil does. in my opinion the only shocks that can be compared to this one is ccdb with a titanium coil (ccdb air is trash for FR/DH), or the dhx rc4 with a titanium coil as well. they wont even come close to weighing the same as the vivid air if you dont get the titanium coil. which is another 250 bucks on top of the shock. that will bring you close to 650 if you get lucky and find a used dhx rc4 for like 400 bucks in good condition. i bought my vivid air brand new for 480 mid tune.