Is the Arcana Skill capable of influencing or affecting actual spells being cast or other spell-centred details? For example, are you able to influence the effect or characteristics of a spell by rolling a high enough Arcana check? Or does that fall primarily within relation to magic items and not cast spells?
According to the D&D 5e Basic Rules (as published on D&D Beyond), Arcana is defined as:
Your Intelligence (Arcana) check measures your ability to recall lore about spells, magic items, eldritch symbols, magical traditions, the planes of existence, and the inhabitants of those planes.
Any usage other than that would be purely up to your DM, but as described above, you could use your proficiency in Arcana to identify a spell or know lore about it, but not to cast or modify it in any way.
The closest to this the Arcana skill has is to identify a spell being cast
With the arcana ability, one can deduce what spell is being cast or has been cast. From Xanathar's Guide to Everything, pg. 85, under "Identifying a Spell":
Sometimes a character wants to identify a spell that someone else is casting or that was already cast. To do so, a character can use their reaction to identify a spell as it's being cast, or they can use an action on their turn to identify a spell by its effect after it is cast.
If the character perceived the casting, the spell's effect, or both, the character can make an Intelligence (Arcana) check with the reaction or action. The DC equals 15 + the spell's level. If the spell is cast as a class spell and the character is a member of that class, the check is made with advantage.
Informative wizard companion
In practice, this can be useful for a companion of a wizard to identify a spell as it's being cast to shout in order to inform the wizard to use their reaction to cast counterspell. In this way, the Arcana skill can be used to facilitate when to know when to
modify counter a spell being cast.