Do small apps need an MMP at all?
If you buy installs from more than one network, yes, because each network will otherwise claim credit using its own rules and the sum will exceed reality. Both AppsFlyer and Adjust offer free tiers that cover small volumes, so cost is no longer the barrier it once was. Apps running only Apple Ads or only organic can defer the decision.
Does Adjust being owned by AppLovin actually matter?
It depends on your risk posture. Adjust operates with contractual data separation from AppLovin's ad business, and no public evidence shows misuse. But if AppLovin is one of your largest UA channels, your measurement vendor and your media seller share an owner, which some advertisers exclude on principle during procurement. Teams that care most tend to be large spenders with leverage; smaller teams typically accept the assurances.
How painful is switching MMPs?
Plan for a full SDK release cycle plus several weeks of parallel running. You will re-implement event mapping, partner postbacks, and SKAN conversion values, and historical data does not migrate, so cohort comparisons break at the cutover. Most teams that switch do it at a natural boundary, such as a major app relaunch or contract renewal, and run both SDKs briefly to validate parity before turning the old one off.