You can get a cheap stick-on elevated flipper rest for less than $20, and see if you like it. My experience is that an elevated rest generally works better with 3 under than split. This is because trad bows are designed to be gripped and pulled from a certain place on the string, and are usually designed for a split grip, unless the buyer requests 3 under. When you grip a bow 3 under, you’re pulling from a slightly lower place on the string, and sometimes putting on an elevated rest moves the 3 under grip back up the string closer to where it should be. I don't really see any tuning advantages in an elevated rest if the bow was designed for split and you're shooting split. However, bows vary and it doesn't hurt to experiment.
An elevated rest allows you to shoot with plastic vanes, if you want to. It puts the arrow further away from your bow hand, which exaggerates the effect of canting the bow. It is a little less natural to nock an arrow on an elevated rest, but people get used to it.