Ranked in these QuestionsQuestion Ranking
Pro iOS and Android support
Pro 10 minute timeline
The free version has a 10 minute timeline, which should be enough for a reaction video.
Pro Supports up to 1 GB files
In free plan, Loopster supports files up to 1 GB in size. This should be more than enough for a reaction video.
Con Free version limits to 480p with a watermark
One needs to buy the $4/month subscription to have 720p and no watermark.