I sold my silver iPhone XS Max that had all these issues (Video stutter + wifi drops/ LTE issues when 2 SIMS are connected at the the same time), And Right after selling I bought a new gold one, also from Hong Kong with 2 physical SIMs. Exactly same phone, only this time everything works perfect.
No stutter, good reception, super fast phone with no lag.
I would recommend others to do the same without waiting for Apple to release fixes as it can already work now.
Hope this helps someone,
Good luck