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I need to use the T2A encoding along with babel to include some Russian names in an English-language document. However, including

usepackage[T1,T2A]fontenc

in the preamble makes all the text fonts, including English, lighter in weight, as in the following:

documentclass[12pt]article 
usepackagelipsum 
usepackagetimes

usepackage[T1,T2A]fontenc
%usepackage[T1]fontenc

begindocument
Large 
lipsum[1]
enddocument

Compare the preceding output with that from when I use T1 encoding alone:

documentclass[12pt]article 
usepackagelipsum 
usepackagetimes

%usepackage[T1,T2A]fontenc
usepackage[T1]fontenc

begindocument
Large 
lipsum[1]
enddocument

This heavier-weight is what I see when I don't use fontenc at all.

Questions:

1. Why does the T2A encoding cause this?


2. What is the remedy — so that the weight will be the same as normally, when fontenc is not used at all?

Composite solution:

The following was suggested by @Davislor's answer (https://tex.stackexchange.com/a/494900/13492) along with the discussion of Tempora-TLF in https://tex.stackexcange.com/questions/473057/russian-language-bold-font-problem-with-newtxtext.

documentclass[12pt]article 
usepackagelipsum

usepackage[T2A,T1]fontenc
usepackage[russian,main=english]babel 
usepackagesubstitutefont
substitutefontT2ArmdefaultTempora-TLF

usepackage[lucidasmallscale]lucidabr

begindocument
Large 
noindent The names are Russian Алекс'андров, Russian Т'ихонов, and Russian Урыс'oн. 
lipsum[1] 
enddocument

Notice that I'm using now Lucida Bright fonts (the ones my actual, book-length document employs), and even for that the font weight of the Russian names matches that of the surrounding English text — even though the Tempora-TLF fonts were intended for use with others.

In the Modern Toolchain

To answer your second question first, here is what I recommend. If possible, replace fontenc with fontspec and use a modern TrueType or OpenType font.

documentclass[12pt]article 
usepackagebabel
usepackagefontspec
usepackage[paperwidth=11cm]geometry % To fit into the allowed width.

babelprovide[main, import=en]english
babelprovide[import=ru]russian

setmainfontTimes New Roman

begindocument
Large
Fyodor Dostoevsky (foreignlanguagerussianФёдор Достоевский) and
Alexander Pushkin (foreignlanguagerussianАлександр Пушкин).
enddocument

As you can see, that sample uses Times rather than Computer Modern and loads Russian hyphenation patterns. babelprovide[import] converts the font encoding for you. Either choose a font that supports Cyrillic, or use babelfont to change fonts.

Depending on how useful the hyphenation patterns are to you, you might even be able to drop the babel package, and just type in Cyrillic letters. Another method of loading a different font for a different script, which doesn’t require markup in the document body, is ucharclasses, but this doesn’t hyphenate. Also consider usepackagemicrotype in LuaLaTeX to dramatically cut down on the amount of hyphenation your document needs.

In the Legacy Toolchain

If you cannot change to LuaLaTeX or XeLaTeX, you will need to actually fix problem 1. That’s simple. The last encoding you give to fontenc becomes the default encoding. The Times font (ptm*) does not come in T2A, so LaTeX falls back to Computer Modern. PDFLaTeX gives me the following error message on your first MWE:

LaTeX Font Warning: Font shape `T2A/ptm/m/n' undefined
(Font) using `T2A/cmr/m/n' instead on input line 8.

In this case, you want to use only a few Russian names. So, you want to load English as the main language, Russian as a second language, and use babel to switch between the encodings of these two languages. One legacy font based on Times that covers Cyrillic is Tempora.

documentclass[12pt]article 
usepackage[X2, T1]fontenc
usepackagetextcomp
usepackagetempora
usepackage[russian, main=english]babel
usepackage[paperwidth=11cm]geometry % To fit into the allowed width.

begindocument
Large
Fyodor Dostoevsky (foreignlanguagerussianФёдор Достоевский) and
Alexander Pushkin (foreignlanguagerussianАлександр Пушкин).
enddocument

In order to use a font family with an encoding that it does not support, you would need to switch fonts whenever you switch languages. You can do this with the substitutefont package (or by declaring a new textrussian command that changes both the language and the fontfamily). E.g.:

usepackagetempora
usepackagetimes
usepackagesubstitutefont

substitutefontT2AfamilydefaultTempora-TLF

There are not many fonts that support T2A, and nearly all are extensions of an existing font: including Computer Modern Unicode, Tempora (Times), Heuristica (Utopia), DejaVu, Libertine and Gentium.