not apm, but rather, by consistency of ability
no, apm isn't a measure of tech skill. tech skill is defined and measured by how consistently one can perform an action in a given situation, the greater tech skill compared by how much more one can do than another. there really isn't a different way to define it (however, how you practically measure that or qualitatively assess that is open for discussion).
in other words, tech skill is how consistently you can do moves with a character, given the known abilities of a character. for example, if you can shffl nairs with fox 100% of the time on fd by yourself, neat. if you can only pull it off 80% of the time juggling peach across the stage, your tech skill isn't as good as someone who can. but if you and another person can both pull that off 100% of the time, then you have to compare with something quantitatively more difficult (in terms of button pressing speed, timing, and finger movement), like what SW or dark do when shield pressuring with shines jabs and sh'd drills. this also means that, if you can't do the stuff that technical players can, then your success rate is basically 0% for those moves, since you haven't tried or completed them, the moves that you can try being defined as the physical limitations and abilities of the character you're playing.
on the other hand, you don't always have to employ 'tech skill', so it's not always seen - as like with more efficient players. as well, tech skill isn't just attacks, it's also how well someone can space or accurately judge and execute a spacing maneuver, in the moment, and be able to pull it off, consistently (or recover well, like with samus).
therefore, to formally 'quantify it', you could measure percentage of successful attempts one player performs with any given move in any situation. this can be really intricate - or you can just generalize it or qualitatively estimate it by saying 'silentwolf does a lot more things a lot more consistently than most other players: his tech skill is more extensive and proficient than other players,' or 'mang0 has a lot of tech skill, but a lot of it might be seen in more in character control in the technical aspects of baiting and spacing, than in comboes'.
it also differs per character, of course.
