Techniques are affected by damage variance from the weapon. If you had to choose Potency Floor +2.5% or Technique +1% while using a weapon that is EXCLUSIVELY a technique weapon, you should take the +1% Technique. If the multiweapon was a mixed damage type, then the 2.5% potency floor is probably better if you actively use the abilities of the mixed weapon.
On a tangent now... Why sub Techter? The PB Boost isn't that good on Rod or Talis. It's AMAZING on Wand (and other melee options) but the Force bonuses are IMO better as a Techter/Force going either Wand/Rod or Wand/Talis. I do love that Rod counter though with Barta Blot or the Gifoie counters. If your goal is to be a "Pure" Force, then consider Gunner as a sub for the Active PP recovery since that pays out HUGE with the Talis Pillbox.