When I use the OFL font to design a logo or use it in printing, may I change the font shape or outline, such as the font spacing, font-weight?
You can change it however you like. See OFL-FAQ 3.1.
If I change the OFL font shape or outline when using it such as on a logo or a poster, should I also need to put the copyright statement on the logo or poster?
You don’t need to include copyright statements, etc. with things made with the fonts - only if you intend on distributing the fonts themselves. See OFL-FAQ 1.1.
Thank you for the quick clarification!