MOT instructed EVA to put priorities on getting passengers to their destinations for the ones solely operated by EVA. Since CI does not operate TPE-SEA, it's likely this route will not be affected (at least not from the start of the strike). TPE-BKK will likely be affected unless you are on one of the flights bound for Europe, but there are many alternatives to BKK from TPE (CI, TG, CX via HKG etc).

As previously mentioned, there are some sources indicating not all FAs who voted support the decision, but more are worried being isolated if they don't go vote. Though, none of us can vouch this being the case. There are also around ~1300 FAs who did not vote, voted no, or were not in the union, so it's likely the initial operations won't be as severe as you would think. More people are suggesting the strike will not be successful, maybe it won't even start. More to reveal after the supposed 6/20 meeting (not sure LIVE or not).

In case strike does occur: For long haul, one can speculate the flights that will likely be canceled are the multiple flights in LAX and SFO (probably keep 1 each) and then axe the additional frequencies at SEA. If axing LAX and SFO are not enough, then you can expect the new routes will get cut, such as IAH and ORD, then maybe JFK and we will round back to SEA, LAX and SFO. For Europe, the flights that are likely to be gone will first be VIE, then AMS, CDG and LHR. BNE will likely be axed from the initial phase. Regional you can expect cuts from multiple frequency flights such as HKG, MFM, KIX, SEL, TYO, SIN or even some of the restricted flights such as SHA, HAN, SGN.