About Poriņš, not much information is available. He was a pupil of Jevgenij Vitting, and a member of the Liepāja opera, where he is said (by the Latvian radio in a program dedicated to him in 2017) to have sung "only small parts". On the other hand, a knowledgeable Latvian record collector on Youtube said that he sang Cavaradossi and Tonio in Pagliacci (???!!!) in Liepāja, and he is listed as one of only four cast members (and the only tenor) of a Pikovaja dama performance in Liepāja on May 11th, 1939, so he would seem to have sung German (as hard as that is to imagine, judging from his records, where he sounds most definitely like a comprimario). In 1939, he got a contract at the Riga opera house, but I have no idea in which roles he appeared there.
Obviously more important than his stage career was his success on records; he made a lot of them for Bellaccord in Riga, almost exclusively pop trifles and patriotic songs, no opera. This was customary for pre-WWII Latvian singers; so as to appear on record, they had to produce themselves as crooners, since Bellaccord (the Latvian market leader) hardly ever recorded any classical music.
Poriņš left Latvia in 1944, when the Wehrmacht had to withdraw, and went with them to Germany, and a few years later to the USA, where he settled in California, and appeared in concerts and on TV.