One of the neatest things about the current Striking Spell ability is that it makes having a held charge a unique state, which is unique to the Magus in 2e. Think of it like Panache. Since you aren't beholden to discharging it as part of the casting action (like in 1e), this opens up a lot more tactical options and synergistic feat options. Consider these scenarios, where I'll use everyone's favorite vanilla option, Shocking Grasp with Slide Casting:
Begin turn outside an enemy's reach. 2 Actions: Cast shocking grasp with Striking Spell. Use slide casting synthesis to free move into melee range. 1 Action: Combat Assessment to strike the enemy and also gain information about their weaknesses. Better yet, if you have haste or hasted assault, 1 Action Feint and then Quickened 1 Action Strike.
Begin turn in melee range. 2 Actions: Cast shocking grasp, but use Slide casting to move out of melee range first. 1 Action: Demoralize, weakening enemies for your allies. Next turn: 1 Action: position yourself in melee, with 2 enemies adjacent. 2 Actions: Spell Swipe, getting 2 max level shocking grasps for 1 spell slot!
There's a lot of getting hung up on the fact that this thing named Striking Spell doesn't behave exactly like the 1e ability named Spellstrike, which *both* gave you a free attack *and* removed the need for a separate attack roll from the spell, either of which would be extremely strong abilities in 2e. There is a way cooler design space to consider if you aren't stuck discharging the spell as part of the cast action.
Rather than combining this all into a single boring probably 3-action activity that you'll be doing every turn to be balanced, let's consider abilities that might come from feats or features that interact well with the Stored Spell state. Maybe something like:
Conduit Strike
Feat 1
1-Action
*Requirements* You have a spell stored in your weapon or body from Striking Spell, and it requires a spell attack roll.
Using your weapon or body as a conduit, you channel your spell to strike true. Make a Strike with the weapon/body storing the spell. If it hits, you gain a +1 status bonus to hit with the stored spell. At level 5 this bonus increases +2, and at level 15 it increases to +4.
Or if you like high-stakes gambling:
Desparate Discharge
1-Action
*Requirements* You have a spell stored in your weapon or body from Striking Spell, and it requires a spell attack roll.
Make a Strike with the weapon/body storing the spell. Use the result of the Strike's attack roll in place of the Spell Attack roll normally required by the spell. If the attack misses, the stored spell is discharged with no effect.
Abilities like this start to get to the feeling of the 1e ability, while also playing nice with the stored spell state, which is the ability unique to the magus class in this playtest. They don't meanwhile limit the design space for other martial abilities like Spell Swipe that also want to make use of it.
divorce the idea that its not with hte *power budget* to improve upon the ability without nerfing it.
if you attack with a spell via spellstrike, apply your item bonus potency runes to the hit/save dc of the spell.
no nerf needed, is it above the supposed, imaginary power budget? sure, does that matter? no, what matters is if its consistent.
Sure I'm not arguing that the base ability's exact power level is perfect. Maybe add the item bonus to spell attack rolls or have it act as a penalty on saves for non-attack roll spells. Just that the implementation as a free action metamagic ability is much more interesting than just stacking every desirable mechanic into a single activity that will probably have to be 3 actions.
Would I be able to store the spell and still make Strikes and also cast Spells as well or just Strikes or nothing but movement/non-attacks?