[M]ost pack makers are taking file size into account when making the packs
Yeah, it's a losing battle.
If you make the videos above 720, people complain that the pack size is too large.
A 1080 webm is about 11-12 MB at 30 seconds; 720 is about 6 MB. It's about a gig when you're throwing 50-70 files in a pack and that makes downloading from Mega a problem since free users are limited to 5 GB per 24 hours.
If you drop the number of files in a pack or shorten the length of the clip, people complain about a lack of variety.
If you give variety and keep the pack size manageable, you get complaints about quality.
Best I can advise: If you see a pack that's between 200-600 MB, the pack is probably 720 or lower (or has only 1 or maybe 2 clips for each category); if it's a gig or bigger, you're probably looking at 1080 resolution (or the packmaker has put 7-10 clips in each category).
Pick your packs accordingly.