The difference between Tower Witches and Studio Witches are pretty varied. Don't why how got names but might be revealed later. Could be for Tower Witches their predecessors lived in towers way back when due to being more convenient than houses for some reason while Studio Witches wanted a more modernish term for those working together in the same permanent workshop. Both usually have a medium or specification causing any medium or high degree of magic they use to have to work with or through it. Whether this is due to personality, skills or something else is unknown. Ayaka, for example, has to use flames for her magic whether it's for healing or attacking. Tanpopo has to use rabbit shaped shikigami which is why when ganging up against Ayaka she had opened her robe to reach for a paper doll rabbit to use. However, weak or basic spells don't seem to be under this restriction as Ayaka was able to stand and fly on a broom without fire. Unless Tanpopo used the rabbit the MC was holding as a medium she was able to cast an illusion of the school building falling without using a rabbit.
Tower witches, or at least ones shown so far, seem to be wanderers without a permanent (or at least someplace not worried about guarding,) base seeking things to power up with or for selfish reasons. Are of evil alignment to a degree, so could be bullying subordinates like these five to a calculating psychopath who uses etiquette and civility to hide a lack of morals or humanity like Professor Moriaty from Sherlock Holmes. More of a collection of independents pursuing their own goals and occasionally teaming up for mutual gain but not monotheistic. Don't really have rules to follow (other than what the group's Master decides,) other than might makes right so either force your opinion or get out of the way. Seems to follow old fashioned Master/Apprentice style where the Master teaches various skills and magic to the Apprentices who in turn pay back the favor by being the Master's subordinates and lackeys. Unknown if for fixed period of time, until Master decides to let them go rather than kill them, subordinate says goodbye and leaves amicably, or subordinate has to defeat/kill Master. Tower Witches can only use their own magic/power for their spells so on own if get into trouble until backup shows up, if it's coming.
Studio Witches are like a semi-monotheistic guild, police force and/or company of witches with a permanent base (the Studio) in several cities who hide their existence from the average citizen while providing protection from magical threats whether other witches or something else. Unknown if there is a President type figure at the top as hasn't been shown yet or if different branches with different rules like difference between CIA, FBI, State Troopers and the local police. Alignment mostly towards good, but can have some oddball characters as well. For example Kazane could have a hobby of torture that's well known, Ayaka doesn't hold back against enemies, and one of the strong fighters is a delinquent (will meet her later.) So like a company or agency everybody is trying to do good mostly, just there are various ideas of what constitutes good or how to handle things. Head of the city's Studio is Kagari Kazane, Ayaka's mother. As the head she not only supervises but continuously provides magic to a citywide barrier that provides magic to Studio Witches and magic protection to average citizens. This means a Studio Witch can use their own magic buffed by the Head's magic making them stronger than a Tower Witch in the city. However, if the Head is suddenly unable to provide magic for some reason, like finally ran out of magic or some big magical commotion caused the barrier to drain too much too quickly, the recoil will knock her out and prevent the other Studio Witches from being able to cast spells for x amount of time. This can be shortened by the Head either recovering and fueling the barrier again or is replaced by someone with a lot of magic power who has enough to sustain the barrier. Tower Witches won't receive any demerits from barrier failing and will still be able to use magic. Unknown if Studio Witches will be able to recover on their own to use magic again if enough time passes or not. As for protection towards citizens it's not absolute and only provides magic protection to a degree. So if someone is hit by a car the barrier does nothing. However, a runaway fireball spell will be mitigated either enough to preserve person's life or prevent them from noticing they got a hit by a fireball depending on strength of fireball. Some things can't be blocked such as Medusa's petrifying magic although it might be able to keep them alive long enough to be turned back from stone to flesh.