Hi, 
Thank you for your comments. For Latvian, I used translations mades with DeepL translator engine and the - I realize this isn't accurate enough and am open to suppress the few choices I offered for Riga streets. 
For Russian names, the choices are made on the detailed informations found in the wikipedia pages in Russian language (a language I read proficiently). Sometimes the edit aren't obvious but I can explain the two examples you give. 
Балтийский бульвар : the WP page give a quote from the SPb toponymic commission stating that the name was giving to this street "because it's running along the Gulf of Finland" (https://ru.wikipedia.org/wiki/%D0%91%D0%B0%D0%BB%D1%82%D0%B8%D0%B9%D1%81%D0%BA%D0%B8%D0%B9_%D0%B1%D1%83%D0%BB%D1%8C%D0%B2%D0%B0%D1%80#cite_note-4). Baltic sea could be seen as a better choice, though. I agree, it's debattable.
For "проспект Строителей" there is no obvious choice. It goes along with other Soviet street names referring to the workers of various economic branches. I chose to give the reference to the economic branch that was cited through the term Строитель. But I agree Q3875186 (construction) would be a better choice, I probably missed the entry.