Why not do both? Level multiple characters, one now, others later.
I've got one of each unleveled allied race started, for example.
After, it much much faster.
Dunno what impact zombie shenanigans will have though as the event is very disruptive to normal play, but then its only around for a few weeks so it might be better to just imurse your self in killing the living and do leveling once so launches as going 0 to max is much much faster than currently on live
I'd get that 98 to 120 before pre-patch so you can have choices when you decide to start from level 1. Otherwise you're gonna be stuck with BFA leveling (unless that's your cup of tea). I leveled one last character from lvl 1 a week ago and am going to wait for pre-patch before I do anything else.
This question reminds me of that scene between Squidward and Mr Krabs:
Squidward: "Why do today, what you can put off till tomorrow?"
Mr Krabs: "What is today, but yesterday's tomorrow?"
One thing to keep in mind - iirc they said that to get the heritage armor for allied races after the prepatch you'll need to level to 60, while atm you only need 110. 110 now with exp bonus is most certainly faster than level 60 in SL.
I'm racing against time to level all the toons I need to 110/120 before pre-patch and the 100% buff goes away. It's fun to set a goal. I'm enjoying leveling my many alts so much right now, I wish Shadowlands wasn't coming out until 2021. I still have Dwarves, Dark Irons, Highmountain, Vulpera, and Nightborne heritage armors left to unlock.
The only alts I'd level now are 110 characters, & the only reason I'd do that is Freehold boosting. It's not really all that doable in the prepatch, but right now, a geared player can two-pull the instance upto the reset point under the bridge. 110-120 takes 40-60 minutes depending on the booster/rested exp.
personnaly i wait the prepatch, people said it will be faster, i have some at level 1 now, a majority are 100/110
and it will be more fun to choice your expansion to do
lk will be not my better choice that said.... i always hated the 58-70 contents in lk for alts, for a strange reasons, it take a lot of time