The official ti.admob module currently does not allow you to fully exploit the potential of AdMob and the various ads formats.
There are important PR to implement rewarded videos that are still in the works for a long time.
Meanwhile, a new rewarded video format has also been released.
Instead the Native Ads format has never been implemented.
It is currently difficult to use the module. The iOS and Android APIs are different, and also change based on the version. Furthermore it is necessary to use other modules to use rewarded videos and native ads.
Could it be easier to create a new module using Hyperloop? Two years ago an android AdMob module (https://github.com/hyperloop-modules/titanium-admob) was started using hyperloop, and apparently it seems simpler.