Subject Charset and Font Character Set for IBX TIBDatabase component

IBExpert uses two settings for database charsets:
- Charset (apparently Database related) and
- Font Character Set (apparently Client related)

As I understand then Charset is the same setting as lc_ctype=UNICODE_FSS in TIBDatabase.Params parameters. But how can I indicate Font Character Set in my Delphi XE10 IBX program that uses TIBDatabase?

I have problem with legacy Firebird 1.5 character set NONE database. When my program is run on Baltic (default windows locale for non-unicode program) computer then the same character is reported as \u0101 (that is correct) but when my program is run no Russian computer then the same character is reported as \u0432 (incorrect). What happens here and how to configure TIBDatabase to work correctly on computers with any locale for non-unicode program?