Keep in mind that the wax rings and flanges are designed to mate properly when the toilet flange is mounted on TOP of the finished floor. Adding tile and a backer board, and maybe some ply to strengthen the floor would mean the flange is now recessed, maybe a fair amount. Ideally, you'd move the flange after tiling. A less desireable thing is to add extention rings. The last choice would be thick wax rings.
When installed per design, the wax ring is squished down to a thin layer. As the flange gets futher from the toilet horn (as when it is recessed in the floor), that area gets filled with wax. Wax isn't as strong in a thick layer as a thin one surrounded by hard materials. Aggressive plunging could cause a blowout, or things might slip during installation, creating problems.