Paid tier includes "free" access to their stock (Storyblocks) media. It is somewhat cheaper to get a Storyblocks video subscription through Clipchamp than through Storyblocks themselves.

I presume at some point 4K will be added, but given that YouTube metrics show that 4k media is still very niche (1080p is something like 85% of viewing), I can see why that might not be top of mind for this.