It really depends on how much time matters to you. If you enjoy playing resto, you will be more than ok leveling as resto (especially if you go in with like 720+ gear). If you start early and keep going you will probably finish leveling in one or two days. If you must be done in half a day because omg need to be level 110 on Tuesday afternoon, you could consider leveling as dps or grouping up with others.
Edit: to answer a bit more. Alpha leveling was a bit different since they released zone after zone. People would be 108 after two zones.
Edit 2: Enjoy the leveling process. Only once will be the first time, and you’ll get to soak up all that the Broken Isles has to offer. Especially this expansion is all about exploration and discovery through multiple activites. Being resto works with that: you’ll heal dungeons etc. Be honest.. are you in a rush to hit 110 halfway on Tuesday or not. That should answer the need to deal with half-half specs while leveling.