Finally, I got everything working.
Correct approach was to create a default font collection,
add several fonts into it from resource stream, set this
collection as default one, and select each font via
xxx.FontName
referring to its internal name (not file name nor resource name).
Also, too many ways to draw text make things a bit complicated
for beginners. These ones are:
BGRABitmap.TextOut (...)
BGRAFreeTypeDrawer.DrawText (...)
BGRAVectorizedFontRenderer.TextOut (...)
BGRATextEffect.Draw (...)
Now I use the 4th variant, but it could be interesting to learn
the difference. What I discovered for now:
1) can draw shadow, can't use stream font;
2) can't draw shadow, can use stream font;
3) can draw shadow, can't use stream font;
4) can draw shadow, can use stream font.
Hope it will be useful to know that for somebody.
Thank you again for your inestimable work!