Such final consonants are often just "stops" so you hardly hear them. For example, my girlfriend's first name is Ngọc; that final c sounds more like a "swallowed" b than like a c. So it's quite normal, I think, for the final c of các to sound more like a "cut-off" than like an actual c...
you would use "ủng hộ" more likely but not exclusively for mental or psychological support. eg. a fan cheering on their idol, their favourite sport team; a person/group/party of influence favoring one side over another; people contributing to a charitable cause; etc. synonyms: to support, to back, to cheer on, to encourage
you would use "hổ trợ" for material support. eg. a patron funding artists; a brand sponsoring a star; the army backing up the authorities during natural disasters; etc. synonyms: to support, to help, to give assistance