The units that are affected are often denoted with the terms team and field. (Field also sometimes seen as lineup.) Team refers to your individual set of ninjas whereas field is all 3 combined teams on your side. In short team is your small squad whereas field is the collective group of teams.
1) Barriers buff differently depending on ninja. Older ninja buff your team only and kage pack ninjas are entire field. (Noobity's video clearly shows this as a great reference.)
2) Ninja such as FKS Temari, Baki and Chojuro buff only in the team they are on. Note: They do not increase their own stats for each ninja they buff their allied units of same team by said percentage. Other ninjas that have buffs, that are not field effects, that span across the entire field are often limited to a set number rather than the entirety of your field, such as Konan buffing 9 akatsuki ninja or Bee buffing 9 jinchuriki.
3) In regard to the above statement, a select few ninjas buff themselves based off of the number of units you have within their team. Swimsuit Ino is one example as she gets increased defense and resistance for every male on her team. The wind mains empress ability is similar in that it gives her increased stats for female ninja on her team.
When done in this way it is possible to stack nearly all your buffs on one team, if you target said team with the other supporting lineups, but there are also drawbacks as then these other teams often don't get as many buffs themselves. It c*so be highly difficult to coordinate this outside of ranked battles as you would then need to coordinate very well with your other two party members.