Let the rails do the work, on3p skis come factory detuned anyway, seriously dont fuck your edges up earlier than they need to be fucked its not work it. just slide the rails properly and you wont have aproblem
Yes either have a shop do it or do it yourself with a. Gummy stone or file if you plan on hitting any rails or boxes I would highly reccomend it it prevents edge cracks from quickly happening making your skis last longer
do not leave it alone underfoot. it fucking sucks to slide rails with sharp edges i have no idea why anyone would recommend that unless you dont plan on skiing park/rails. the edges will be more prone to edgecracks and they will catch and hook like a bitch.