limitation of playing strength for chess engines

[Norbert Raimund Leisner]

Hello,

after embedding of external WB/UCI engines into ScidvsPC https://sourceforge.net/projects/scidvspc/files/ after Tools>Analysis Engines>New etc. appears an application "Configure Engine" with a field for input of the rating (Elo points). Is this configuration a real limitation of playing strength for engines or has it no bearing on the process of a match "engine X vs. engine Y"?

Engine "Bringer" has a playing-strength limit for its own interface.
http://chess.kearman.com/bringer/bringer-index.html - http://scacchi.qnet.it/software/bringer.htm

Is just an adjustment possible too if it plays as WinBoard-compatible program with WinBoard-Interface?

Do you know an enumeration of chess engines with adjustable playing strength?

Best wishes,
Norbert