yes, current DTVS would be honoured. The DTV is more likely to be revised, having some form of a diginomad visa is key for Thailand to remain competitive v other countries
All embassies approve DTV dependents the 500K THB requirement differs among embassies though. You should check the main DTV FB group, lots of posts about this topic.
They will ask you for any docs they need. A portfolio is very open ended it can include a resume, sample of work, client letter/emails of appreciation etc