Here are some clarifications on support for 32-bit and 64-bit architectures, that are included in the Wikitude SDK.
Wikitude started early to include dedicated 64-bit versions (arm64, armv8 architecture) of the Wikitude SDK for both iOS and Android. Apple started to require 64-bit libraries for App Store submissions back in 2015, Google started to require them now in 2019 for submissions in Google Play.
Android - Unity
It took Unity a little bit longer to fully support 64-bit for Android. With Wikitude SDK 8.0 (July 2018), the Unity plugin is ready to work with 64-bit version but needs some manual configuration, with Wikitude SDK 8.4 (April 2019) the Unity plugin is by default configured for support of 64-bit. You can find further details on how modifications needed here:
Android - Intel