generally many players go for phalanx 2 (challenge quests) to farm affection because it also drops plat fairy which is an important combination unit to multiply the exp you get from plat armors to level up plat units (majority of the event units are plats)
however, affection daily itself isn't all that bad because H gives guaranteed 3 bouquets and has a rather high chance of getting the higher tier affection items as well. phalanx 2 has average of ~1.8 aff/stamina while wed daily has average of 3+ aff/stamina. (the charisma cost is a pain though)
in videos, they don't use max because chances are that team is just an alt they use for making videos and level 50 will be sufficient. any higher and the minor stat boost may screw newbies following the videos over. also cost effectiveness is one point although most players would suggest getting 1 unit to 50cc30 or 50cc40 and working on the rest of the team until your core units are all 50cc40 at the minimum.